45 lines
1.9 KiB
Forth
45 lines
1.9 KiB
Forth
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#version 100
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#extension GL_OES_standard_derivatives : enable
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precision highp float;
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#define M_PI 3.1415926535897932384626433832795
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// 2D texture (1D texture split by the rows) of color along the object Z axis.
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uniform sampler2D z_texture;
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// Scaling from the Z texture rows coordinate to the normalized texture row coordinate.
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uniform float z_to_texture_row;
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uniform float z_texture_row_to_normalized;
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uniform float z_cursor;
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uniform float z_cursor_band_width;
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// x = tainted, y = specular;
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varying vec2 intensity;
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varying float object_z;
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void main()
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{
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float object_z_row = z_to_texture_row * object_z;
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// Index of the row in the texture.
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float z_texture_row = floor(object_z_row);
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// Normalized coordinate from 0. to 1.
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float z_texture_col = object_z_row - z_texture_row;
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float z_blend = 0.25 * cos(min(M_PI, abs(M_PI * (object_z - z_cursor) * 1.8 / z_cursor_band_width))) + 0.25;
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// Calculate level of detail from the object Z coordinate.
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// This makes the slowly sloping surfaces to be shown with high detail (with stripes),
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// and the vertical surfaces to be shown with low detail (no stripes)
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float z_in_cells = object_z_row * 190.;
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// Gradient of Z projected on the screen.
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float dx_vtc = dFdx(z_in_cells);
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float dy_vtc = dFdy(z_in_cells);
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float lod = clamp(0.5 * log2(max(dx_vtc * dx_vtc, dy_vtc * dy_vtc)), 0., 1.);
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// Sample the Z texture. Texture coordinates are normalized to <0, 1>.
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vec4 color = vec4(0.25, 0.25, 0.25, 1.0);
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if (z_texture_row >= 0.0)
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color = mix(texture2D(z_texture, vec2(z_texture_col, z_texture_row_to_normalized * (z_texture_row + 0.5 )), -10000.),
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texture2D(z_texture, vec2(z_texture_col, z_texture_row_to_normalized * (z_texture_row * 2. + 1.)), 10000.), lod);
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// Mix the final color.
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gl_FragColor = vec4(vec3(intensity.y), 1.0) + intensity.x * mix(color, vec4(1.0, 1.0, 0.0, 1.0), z_blend);
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}
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