Use Vertex Buffer Objects for rendering of 3D volumes if possible.

lib/Slic3r/GUI/3DScene.pm

@@ -540,6 +540,10 @@ sub mouse_wheel_event {
 # Reset selection.
 sub reset_objects {
     my ($self) = @_;
+    if ($self->{use_VBOs}) {
+        $self->GetContext;
+        $self->volumes->release_geometry;
+    }
     $self->volumes->erase;
     $self->_dirty(1);
 }
@@ -944,6 +948,10 @@ sub InitGL {
     return unless $self->GetContext;
     $self->init(1);
 
+    my @gl_version = split(/\./, glGetString(GL_VERSION));
+    $self->{use_VBOs} = int($gl_version[0]) >= 2;
+#    print "OpenGL major: $gl_version[0], minor: $gl_version[1]. Use VBOs: ", $self->{use_VBOs}, "\n";
+
     glClearColor(0, 0, 0, 1);
     glColor3f(1, 0, 0);
     glEnable(GL_DEPTH_TEST);
@@ -983,12 +991,15 @@ sub InitGL {
     glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);
     glEnable(GL_COLOR_MATERIAL);
     glEnable(GL_MULTISAMPLE);
+
+    Slic3r::GUI::_3DScene::_glew_init;
 }
 
 sub DestroyGL {
     my $self = shift;
     if ($self->init && $self->GetContext) {
         delete $self->{shader};
+        $self->volumes->release_geometry;
     }
 }
 
@@ -1251,58 +1262,7 @@ sub draw_volumes {
             glColor4f(@{ $volume->color });
         }
 
-        glPushMatrix();
+        $volume->render;
-        glTranslatef(@{$volume->origin});
-        glCullFace(GL_BACK);
-    if (1) {
-        if ($volume->indexed) {
-            my $quads_cnt = $volume->indexed_quads_to_render_cnt;
-            my $triangles_cnt = $volume->indexed_triangles_to_render_cnt;
-            if ($quads_cnt + $triangles_cnt > 0) {
-                if ($self->{use_VBOs}) {
-                    my ($name_geometry, $name_triangle_indices, $name_quad_indices) = glGenBuffersARB_p(3);
-                    glBindBufferARB(GL_ARRAY_BUFFER_ARB, $name_geometry);
-                    glBufferDataARB_c(GL_ARRAY_BUFFER_ARB, $volume->geometry_size, $volume->triangles_to_render_ptr, GL_STATIC_DRAW_ARB);
-                    glInterleavedArrays_c(GL_N3F_V3F, 0, 0);
-                    if ($quads_cnt) {
-                        glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, $name_quad_indices);
-                        glBufferDataARB_c(GL_ELEMENT_ARRAY_BUFFER_ARB, $volume->indexed_quads_cnt * 4, $volume->quad_indices_ptr, GL_STATIC_DRAW_ARB);
-                        glDrawElements_c(GL_QUADS, $quads_cnt, GL_UNSIGNED_INT, $volume->quad_indices_to_render_offset * 4);
-                    }
-                    if ($triangles_cnt) {
-                        glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, $name_triangle_indices);
-                        glBufferDataARB_c(GL_ELEMENT_ARRAY_BUFFER_ARB, $volume->indexed_triangles_cnt * 4, $volume->triangle_indices_ptr, GL_STATIC_DRAW_ARB);
-                        glDrawElements_c(GL_TRIANGLES, $triangles_cnt, GL_UNSIGNED_INT, $volume->triangle_indices_to_render_offset * 4);
-                    }
-                    glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
-                    glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
-                    glDeleteBuffersARB_p(($name_geometry, $name_triangle_indices, $name_quad_indices));
-                } else {
-                    glInterleavedArrays_c(GL_N3F_V3F, 0, $volume->triangles_to_render_ptr);
-                    glDrawElements_c(GL_QUADS,     $quads_cnt,     GL_UNSIGNED_INT, $volume->quad_indices_ptr     + $volume->quad_indices_to_render_offset     * 4)
-                        if ($quads_cnt);
-                    glDrawElements_c(GL_TRIANGLES, $triangles_cnt, GL_UNSIGNED_INT, $volume->triangle_indices_ptr + $volume->triangle_indices_to_render_offset * 4)
-                        if ($triangles_cnt);
-                    glInterleavedArrays_c(GL_N3F_V3F, 0, 0);
-                }
-            }
-        } elsif (! $volume->empty) {
-            if ($self->{use_VBOs}) {
-                my ($name_geometry) = glGenBuffersARB_p(1);
-                glBindBufferARB(GL_ARRAY_BUFFER_ARB, $name_geometry);
-                glBufferDataARB_c(GL_ARRAY_BUFFER_ARB, $volume->triangles_to_render_cnt * 6 * 4, $volume->triangles_to_render_ptr, GL_STATIC_DRAW_ARB);
-                glInterleavedArrays_c(GL_N3F_V3F, 0, 0);
-                glDrawArrays(GL_TRIANGLES, 0, $volume->triangles_to_render_cnt);
-                glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
-                glDeleteBuffersARB_p(($name_geometry));
-            } else {
-                glInterleavedArrays_c(GL_N3F_V3F, 0, $volume->triangles_to_render_ptr);
-                glDrawArrays(GL_TRIANGLES, 0, $volume->triangles_to_render_cnt);
-                glInterleavedArrays_c(GL_N3F_V3F, 0, 0);
-            }
-        }
-    }
-        glPopMatrix();
 
         if ($shader_active) {
             glBindTexture(GL_TEXTURE_2D, 0);

xs/src/glew/src/glew.c

@@ -174,7 +174,7 @@ void* NSGLGetProcAddress (const GLubyte *name)
 #if defined(GLEW_REGAL)
 #  define glewGetProcAddress(name) regalGetProcAddress((const GLchar *) name)
 #elif defined(_WIN32)
-#  define glewGetProcAddress(name) ((LPCSTR)name)
+#  define glewGetProcAddress(name) wglGetProcAddress((LPCSTR)name)
 #elif defined(__APPLE__) && !defined(GLEW_APPLE_GLX)
 #  define glewGetProcAddress(name) NSGLGetProcAddress(name)
 #elif defined(__sgi) || defined(__sun) || defined(__HAIKU__)
@@ -12105,8 +12105,10 @@ GLenum GLEWAPIENTRY wglewInit (WGLEW_CONTEXT_ARG_DEF_LIST)
       extStart = (const GLubyte*)"";
     else
       extStart = (const GLubyte*)_wglewGetExtensionsStringEXT();
-  else
+  else {
-    extStart = (const GLubyte*)_wglewGetExtensionsStringARB(wglGetCurrentDC());
+    HDC dc = wglGetCurrentDC(); 
+    extStart = (const GLubyte*)_wglewGetExtensionsStringARB(dc);
+  }
   extEnd = extStart + _glewStrLen(extStart);
   /* initialize extensions */
   crippled = _wglewGetExtensionsStringARB == NULL && _wglewGetExtensionsStringEXT == NULL;

xs/src/libslic3r/EdgeGrid.cpp

@@ -1353,7 +1353,7 @@ Polygons EdgeGrid::Grid::contours_simplified(coord_t offset) const
 	return out;
 }
 
-#ifdef SLIC3R_GUI
+#if 0
 void EdgeGrid::save_png(const EdgeGrid::Grid &grid, const BoundingBox &bbox, coord_t resolution, const char *path)
 {
 	unsigned int w = (bbox.max.x - bbox.min.x + resolution - 1) / resolution;

xs/src/libslic3r/EdgeGrid.hpp

@@ -107,7 +107,7 @@ protected:
 	std::vector<float>							m_signed_distance_field;
 };
 
-#ifdef SLIC3R_GUI
+#if 0
 // Debugging utility. Save the signed distance field.
 extern void save_png(const Grid &grid, const BoundingBox &bbox, coord_t resolution, const char *path);
 #endif /* SLIC3R_GUI */

xs/src/libslic3r/SupportMaterial.cpp

@@ -940,7 +940,7 @@ PrintObjectSupportMaterial::MyLayersPtr PrintObjectSupportMaterial::bottom_conta
                 ::Slic3r::SVG svg(debug_out_path("support-bottom-contacts-simplified-%d-%d.svg", iRun, layer_id), bbox);
                 svg.draw(union_ex(projection, false), "blue", 0.5);
                 svg.draw(union_ex(projection_simplified, false), "red", 0.5);
-    #ifdef SLIC3R_GUI
+    #if 0
                 bbox.min.x -= scale_(5.f);
                 bbox.min.y -= scale_(5.f);
                 bbox.max.x += scale_(5.f);

xs/src/slic3r/GUI/3DScene.cpp

@@ -1,3 +1,5 @@
+#include <GL/glew.h>
+
 #include "3DScene.hpp"
 
 #include "../../libslic3r/libslic3r.h"
@@ -21,6 +23,10 @@ namespace Slic3r {
 
 void GLIndexedVertexArray::load_mesh_flat_shading(const TriangleMesh &mesh)
 {
+    assert(triangle_indices.empty() && vertices_and_normals_interleaved_size == 0);
+    assert(quad_indices.empty() && triangle_indices_size == 0);
+    assert(vertices_and_normals_interleaved.size() % 6 == 0 && quad_indices_size == vertices_and_normals_interleaved.size());
+
     this->vertices_and_normals_interleaved.reserve(this->vertices_and_normals_interleaved.size() + 3 * 3 * 2 * mesh.facets_count());
     
     for (int i = 0; i < mesh.stl.stats.number_of_facets; ++ i) {
@@ -28,6 +34,130 @@ void GLIndexedVertexArray::load_mesh_flat_shading(const TriangleMesh &mesh)
         for (int j = 0; j < 3; ++ j)
             this->push_geometry(facet.vertex[j].x, facet.vertex[j].y, facet.vertex[j].z, facet.normal.x, facet.normal.y, facet.normal.z);
     }
+
+    vertices_and_normals_interleaved_size = this->vertices_and_normals_interleaved.size();
+}
+
+void GLIndexedVertexArray::finalize_geometry(bool use_VBOs)
+{
+    assert(this->vertices_and_normals_interleaved_VBO_id == 0);
+    assert(this->triangle_indices_VBO_id == 0);
+    assert(this->quad_indices_VBO_id == 0);
+
+    this->setup_sizes();
+
+    if (use_VBOs) {
+        if (! empty()) {
+            glGenBuffers(1, &this->vertices_and_normals_interleaved_VBO_id);
+            glBindBuffer(GL_ARRAY_BUFFER, this->vertices_and_normals_interleaved_VBO_id);
+            glBufferData(GL_ARRAY_BUFFER, this->vertices_and_normals_interleaved.size() * 4, this->vertices_and_normals_interleaved.data(), GL_STATIC_DRAW);
+            glBindBuffer(GL_ARRAY_BUFFER, 0);
+            this->vertices_and_normals_interleaved.clear();
+        }
+        if (! this->triangle_indices.empty()) {
+            glGenBuffers(1, &this->triangle_indices_VBO_id);
+            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->triangle_indices_VBO_id);
+            glBufferData(GL_ELEMENT_ARRAY_BUFFER, this->triangle_indices.size() * 4, this->triangle_indices.data(), GL_STATIC_DRAW);
+            this->triangle_indices.clear();
+        }
+        if (! this->quad_indices.empty()) {
+            glGenBuffers(1, &this->quad_indices_VBO_id);
+            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->quad_indices_VBO_id);
+            glBufferData(GL_ELEMENT_ARRAY_BUFFER, this->quad_indices.size() * 4, this->quad_indices.data(), GL_STATIC_DRAW);
+            this->quad_indices.clear();
+        }
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    }
+    this->shrink_to_fit();
+}
+
+void GLIndexedVertexArray::release_geometry()
+{
+    if (this->vertices_and_normals_interleaved_VBO_id)
+        glDeleteBuffers(1, &this->vertices_and_normals_interleaved_VBO_id);
+    if (this->triangle_indices_VBO_id)
+        glDeleteBuffers(1, &this->triangle_indices_VBO_id);
+    if (this->quad_indices_VBO_id)
+        glDeleteBuffers(1, &this->quad_indices_VBO_id);
+    this->clear();
+    this->shrink_to_fit();
+}
+
+void GLIndexedVertexArray::render() const
+{
+    if (this->indexed()) {
+        if (this->vertices_and_normals_interleaved_VBO_id) {
+            // Render using the Vertex Buffer Objects.
+            glBindBuffer(GL_ARRAY_BUFFER, this->vertices_and_normals_interleaved_VBO_id);
+            glInterleavedArrays(GL_N3F_V3F, 0, nullptr);
+            if (this->triangle_indices_size > 0) {
+                glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->triangle_indices_VBO_id);
+                glDrawElements(GL_TRIANGLES, GLsizei(this->triangle_indices_size), GL_UNSIGNED_INT, nullptr);
+            }
+            if (this->quad_indices_size > 0) {
+                glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->quad_indices_VBO_id);
+                glDrawElements(GL_QUADS, GLsizei(this->quad_indices_size), GL_UNSIGNED_INT, nullptr);
+            }
+            glBindBuffer(GL_ARRAY_BUFFER, 0);
+            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+        } else {
+            // Render in an immediate mode.
+            glInterleavedArrays(GL_N3F_V3F, 0, this->vertices_and_normals_interleaved.data());
+            // Due to issues with the Intel drivers, rather limit the amount of vertices processed per draw command.
+            if (! this->triangle_indices.empty())
+                glDrawElements(GL_TRIANGLES, GLsizei(this->triangle_indices_size), GL_UNSIGNED_INT, this->triangle_indices.data());
+            if (! this->quad_indices.empty())
+                glDrawElements(GL_QUADS, GLsizei(this->quad_indices_size), GL_UNSIGNED_INT, this->quad_indices.data());
+        }
+    } else {
+        if (this->vertices_and_normals_interleaved_VBO_id) {
+            // Render using the Vertex Buffer Objects.
+            glBindBuffer(GL_ARRAY_BUFFER, this->vertices_and_normals_interleaved_VBO_id);
+            glInterleavedArrays(GL_N3F_V3F, 0, nullptr);
+            glDrawArrays(GL_TRIANGLES, 0, GLsizei(this->vertices_and_normals_interleaved_size / 6));
+            glBindBuffer(GL_ARRAY_BUFFER, 0);
+        } else {
+            // Render in an immediate mode.
+            glInterleavedArrays(GL_N3F_V3F, 0, this->vertices_and_normals_interleaved.data());
+            glDrawArrays(GL_TRIANGLES, 0, GLsizei(this->vertices_and_normals_interleaved_size / 6));
+        }
+    }
+
+    glInterleavedArrays(GL_N3F_V3F, 0, nullptr);
+}
+
+void GLIndexedVertexArray::render(
+    const std::pair<size_t, size_t> &tverts_range,
+    const std::pair<size_t, size_t> &qverts_range) const 
+{
+    assert(this->indexed());
+    if (! this->indexed())
+        return;
+
+    if (this->vertices_and_normals_interleaved_VBO_id) {
+        // Render using the Vertex Buffer Objects.
+        glBindBuffer(GL_ARRAY_BUFFER, this->vertices_and_normals_interleaved_VBO_id);
+        glInterleavedArrays(GL_N3F_V3F, 0, nullptr);
+        if (this->triangle_indices_size > 0) {
+            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->triangle_indices_VBO_id);
+            glDrawElements(GL_TRIANGLES, GLsizei(std::min(this->triangle_indices_size, tverts_range.second - tverts_range.first)), GL_UNSIGNED_INT, (const void*)(tverts_range.first * 4));
+        }
+        if (this->quad_indices_size > 0) {
+            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->quad_indices_VBO_id);
+            glDrawElements(GL_QUADS, GLsizei(std::min(this->quad_indices_size, qverts_range.second - qverts_range.first)), GL_UNSIGNED_INT, (const void*)(qverts_range.first * 4));
+        }
+        glBindBuffer(GL_ARRAY_BUFFER, 0);
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    } else {
+        // Render in an immediate mode.
+        glInterleavedArrays(GL_N3F_V3F, 0, this->vertices_and_normals_interleaved.data());
+        if (! this->triangle_indices.empty())
+            glDrawElements(GL_TRIANGLES, GLsizei(std::min(this->triangle_indices_size, tverts_range.second - tverts_range.first)), GL_UNSIGNED_INT, (const void*)(this->triangle_indices.data() + tverts_range.first));
+        if (! this->quad_indices.empty())
+            glDrawElements(GL_QUADS, GLsizei(std::min(this->quad_indices_size, qverts_range.second - qverts_range.first)), GL_UNSIGNED_INT, (const void*)(this->quad_indices.data() + qverts_range.first));
+    }
+
+    glInterleavedArrays(GL_N3F_V3F, 0, nullptr);
 }
 
 void GLVolume::set_range(double min_z, double max_z)
@@ -65,6 +195,18 @@ void GLVolume::set_range(double min_z, double max_z)
     }
 }
 
+void GLVolume::render() const
+{
+    glCullFace(GL_BACK);
+    glPushMatrix();
+    glTranslated(this->origin.x, this->origin.y, this->origin.z);
+    if (this->indexed_vertex_array.indexed())
+        this->indexed_vertex_array.render(this->tverts_range, this->qverts_range);
+    else
+        this->indexed_vertex_array.render();
+    glPopMatrix();
+}
+
 void GLVolume::generate_layer_height_texture(PrintObject *print_object, bool force)
 {
     GLTexture *tex = this->layer_height_texture.get();
@@ -235,7 +377,6 @@ static void thick_lines_to_indexed_vertex_array(
             idx_a[BOTTOM] = idx_prev[BOTTOM];
         }
 
-        bool sharp = true;
         if (ii == 0) {
             // Start of the 1st line segment.
             idx_a[LEFT ] = idx_last ++;
@@ -490,6 +631,11 @@ static void extrusionentity_to_verts(const ExtrusionEntity *extrusion_entity, fl
     }
 }
 
+void _3DScene::_glew_init()
+{ 
+    glewInit();
+}
+
 // Create 3D thick extrusion lines for a skirt and brim.
 // Adds a new Slic3r::GUI::3DScene::Volume to volumes.
 void _3DScene::_load_print_toolpaths(
@@ -539,6 +685,7 @@ void _3DScene::_load_print_toolpaths(
     auto bb = print->bounding_box();
     volume.bounding_box.merge(Pointf3(unscale(bb.min.x), unscale(bb.min.y), 0.f));
     volume.bounding_box.merge(Pointf3(unscale(bb.max.x), unscale(bb.max.y), 0.f));
+    volume.indexed_vertex_array.finalize_geometry(use_VBOs);
 }
 
 // Create 3D thick extrusion lines for object forming extrusions.
@@ -559,8 +706,10 @@ void _3DScene::_load_print_object_toolpaths(
         bool                         has_infill;
         bool                         has_support;
 
-//        static const size_t          alloc_size_max    () { return 32 * 1048576 / 4; }
+        // Number of vertices (each vertex is 6x4=24 bytes long)
-        static const size_t          alloc_size_max    () { return 4 * 1048576 / 4; }
+        static const size_t          alloc_size_max    () { return 131072; } // 3.15MB
+//        static const size_t          alloc_size_max    () { return 65536; } // 1.57MB 
+//        static const size_t          alloc_size_max    () { return 32768; } // 786kB
         static const size_t          alloc_size_reserve() { return alloc_size_max() * 2; }
 
         static const float*          color_perimeters  () { static float color[4] = { 1.0f, 1.0f, 0.0f, 1.f }; return color; } // yellow
@@ -672,6 +821,8 @@ void _3DScene::_load_print_object_toolpaths(
         volume_ptr += v.volumes.size();
         v.volumes.clear();
     }
+    for (GLVolume *v : volumes->volumes)
+        v->indexed_vertex_array.finalize_geometry(use_VBOs);
   
     BOOST_LOG_TRIVIAL(debug) << "Loading print object toolpaths in parallel - end"; 
 }

xs/src/slic3r/GUI/3DScene.hpp

@@ -17,31 +17,49 @@ class ModelObject;
 // possibly indexed by triangles and / or quads.
 class GLIndexedVertexArray {
 public:
-    GLIndexedVertexArray() {}
+    GLIndexedVertexArray() : 
+        vertices_and_normals_interleaved_VBO_id(0),
+        triangle_indices_VBO_id(0),
+        quad_indices_VBO_id(0)
+        { this->setup_sizes(); }
     GLIndexedVertexArray(const GLIndexedVertexArray &rhs) :
         vertices_and_normals_interleaved(rhs.vertices_and_normals_interleaved),
         triangle_indices(rhs.triangle_indices),
-        quad_indices(rhs.quad_indices)
+        quad_indices(rhs.quad_indices),
-        {}
+        vertices_and_normals_interleaved_VBO_id(0),
+        triangle_indices_VBO_id(0),
+        quad_indices_VBO_id(0)
+        { this->setup_sizes(); }
     GLIndexedVertexArray(GLIndexedVertexArray &&rhs) :
         vertices_and_normals_interleaved(std::move(rhs.vertices_and_normals_interleaved)),
         triangle_indices(std::move(rhs.triangle_indices)),
-        quad_indices(std::move(rhs.quad_indices))
+        quad_indices(std::move(rhs.quad_indices)),
-        {}
+        vertices_and_normals_interleaved_VBO_id(0),
+        triangle_indices_VBO_id(0),
+        quad_indices_VBO_id(0)
+        { this->setup_sizes(); }
 
     GLIndexedVertexArray& operator=(const GLIndexedVertexArray &rhs)
     {
+        assert(vertices_and_normals_interleaved_VBO_id == 0);
+        assert(triangle_indices_VBO_id == 0);
+        assert(triangle_indices_VBO_id == 0);
         this->vertices_and_normals_interleaved = rhs.vertices_and_normals_interleaved;
         this->triangle_indices                 = rhs.triangle_indices;
         this->quad_indices                     = rhs.quad_indices;
+        this->setup_sizes();
         return *this;
     }
 
     GLIndexedVertexArray& operator=(GLIndexedVertexArray &&rhs) 
     {
+        assert(vertices_and_normals_interleaved_VBO_id == 0);
+        assert(triangle_indices_VBO_id == 0);
+        assert(triangle_indices_VBO_id == 0);
         this->vertices_and_normals_interleaved = std::move(rhs.vertices_and_normals_interleaved);
         this->triangle_indices                 = std::move(rhs.triangle_indices);
         this->quad_indices                     = std::move(rhs.quad_indices);
+        this->setup_sizes();
         return *this;
     }
 
@@ -50,8 +68,22 @@ public:
     std::vector<int>   triangle_indices;
     std::vector<int>   quad_indices;
 
+    // When the geometry data is loaded into the graphics card as Vertex Buffer Objects,
+    // the above mentioned std::vectors are cleared and the following variables keep their original length.
+    size_t             vertices_and_normals_interleaved_size;
+    size_t             triangle_indices_size;
+    size_t             quad_indices_size;
+
+    // IDs of the Vertex Array Objects, into which the geometry has been loaded.
+    // Zero if the VBOs are not used.
+    unsigned int       vertices_and_normals_interleaved_VBO_id;
+    unsigned int       triangle_indices_VBO_id;
+    unsigned int       quad_indices_VBO_id;
+
     void load_mesh_flat_shading(const TriangleMesh &mesh);
 
+    inline bool has_VBOs() const { return vertices_and_normals_interleaved_VBO_id != 0; }
+
     inline void reserve(size_t sz) {
         this->vertices_and_normals_interleaved.reserve(sz * 6);
         this->triangle_indices.reserve(sz * 3);
@@ -72,20 +104,33 @@ public:
         push_geometry(float(x), float(y), float(z), float(nx), float(ny), float(nz));
     }
 
+    // Finalize the initialization of the geometry & indices,
+    // upload the geometry and indices to OpenGL VBO objects
+    // and shrink the allocated data, possibly relasing it if it has been loaded into the VBOs.
+    void finalize_geometry(bool use_VBOs);
+    // Release the geometry data, release OpenGL VBOs.
+    void release_geometry();
+    // Render either using an immediate mode, or the VBOs.
+    void render() const;
+    void render(const std::pair<size_t, size_t> &tverts_range, const std::pair<size_t, size_t> &qverts_range) const;
+
     // Is there any geometry data stored?
-    bool empty() const { return vertices_and_normals_interleaved.empty(); }
+    bool empty() const { return vertices_and_normals_interleaved_size == 0; }
 
     // Is this object indexed, or is it just a set of triangles?
-    bool indexed() const { return ! this->empty() && (! this->triangle_indices.empty() || ! this->quad_indices.empty()); }
+    bool indexed() const { return ! this->empty() && this->triangle_indices_size + this->quad_indices_size > 0; }
 
     void clear() {
         this->vertices_and_normals_interleaved.clear();
         this->triangle_indices.clear();
         this->quad_indices.clear();
+        this->setup_sizes();
     }
 
     // Shrink the internal storage to tighly fit the data stored.
     void shrink_to_fit() { 
+        if (! this->has_VBOs())
+            this->setup_sizes();
         this->vertices_and_normals_interleaved.shrink_to_fit();
         this->triangle_indices.shrink_to_fit();
         this->quad_indices.shrink_to_fit();
@@ -109,6 +154,13 @@ public:
         }
         return bbox;
     }
+
+private:
+    inline void setup_sizes() {
+        vertices_and_normals_interleaved_size = this->vertices_and_normals_interleaved.size();
+        triangle_indices_size                 = this->triangle_indices.size();
+        quad_indices_size                     = this->quad_indices.size();
+    }
 };
 
 class GLTexture
@@ -201,23 +253,8 @@ public:
     bool                indexed() const { return this->indexed_vertex_array.indexed(); }
 
     void                set_range(coordf_t low, coordf_t high);
-
+    void                render() const;
-    // Non-indexed interleaved vertices & normals, likely forming triangles.
+    void                release_geometry() { this->indexed_vertex_array.release_geometry(); }
-    void*               triangles_to_render_ptr() { return indexed_vertex_array.vertices_and_normals_interleaved.data(); }
-    size_t              triangles_to_render_cnt() { return indexed_vertex_array.vertices_and_normals_interleaved.size() / (3 * 2); }
-    // Indexed triangles & quads, complete set for storing into a vertex buffer.
-    size_t              geometry_size() const { return indexed_vertex_array.vertices_and_normals_interleaved.size() * 4; }
-    void*               triangle_indices_ptr() { return indexed_vertex_array.triangle_indices.data(); }
-    void*               quad_indices_ptr() { return indexed_vertex_array.quad_indices.data(); }
-    size_t              indexed_triangles_cnt() { return indexed_vertex_array.triangle_indices.size(); }
-    size_t              indexed_quads_cnt() { return indexed_vertex_array.quad_indices.size(); }
-    // Indexed triangles & quads, to be painted in an immediate mode.
-    size_t              triangle_indices_to_render_offset() const { return tverts_range.first; }
-    size_t              quad_indices_to_render_offset() const { return qverts_range.first; }
-    size_t              indexed_triangles_to_render_cnt() const { return std::min(indexed_vertex_array.triangle_indices.size(), tverts_range.second - tverts_range.first); }
-    size_t              indexed_quads_to_render_cnt() const { return std::min(indexed_vertex_array.quad_indices.size(), qverts_range.second - qverts_range.first); }
-
-    void                render_VBOs() const;
 
     /************************************************ Layer height texture ****************************************************/
     std::shared_ptr<GLTexture>  layer_height_texture;
@@ -261,10 +298,14 @@ public:
         const std::string       &select_by,
         const std::string       &drag_by);
 
+    // Release the geometry data assigned to the volumes.
+    // If OpenGL VBOs were allocated, an OpenGL context has to be active to release them.
+    void release_geometry() { for (auto *v : volumes) v->release_geometry(); }
+    // Clear the geometry
     void clear() { for (auto *v : volumes) delete v; volumes.clear(); }
+
     bool empty() const { return volumes.empty(); }
     void set_range(double low, double high) { for (GLVolume *vol : this->volumes) vol->set_range(low, high); }
-    void render_VBOs() const { for (GLVolume *vol : this->volumes) vol->render_VBOs(); }
 
 private:
     GLVolumeCollection(const GLVolumeCollection &other);
@@ -274,6 +315,8 @@ private:
 class _3DScene
 {
 public:
+    static void _glew_init();
+
     static void _load_print_toolpaths(
         const Print         *print,
         GLVolumeCollection  *volumes,

xs/xsp/GUI_3DScene.xsp

@@ -38,17 +38,7 @@
     bool                empty() const;
     bool                indexed() const;
 
-    void*               triangles_to_render_ptr();
+    void                render() const;
-    size_t              triangles_to_render_cnt();
-    size_t              geometry_size() const;
-    void*               triangle_indices_ptr();
-    void*               quad_indices_ptr();
-    size_t              indexed_triangles_cnt();
-    size_t              indexed_quads_cnt();
-    size_t              triangle_indices_to_render_offset() const;
-    size_t              quad_indices_to_render_offset() const;
-    size_t              indexed_triangles_to_render_cnt() const;
-    size_t              indexed_quads_to_render_cnt() const;
 
     bool                has_layer_height_texture();
     int                 layer_height_texture_width();
@@ -74,6 +64,8 @@
         %code{% RETVAL = THIS->volumes.size(); %};
 
     void set_range(double low, double high);
+
+    void release_geometry();    
 %{
 
 SV*
@@ -95,6 +87,12 @@ GLVolumeCollection::arrayref()
 %package{Slic3r::GUI::_3DScene};
 %{
 
+
+void
+_glew_init()
+    CODE:
+        _3DScene::_glew_init();
+
 void
 _load_print_toolpaths(print, volumes, use_VBOs)
         Print               *print;