92 lines
3.1 KiB
GLSL
92 lines
3.1 KiB
GLSL
// version 120 is needed for gl_PointCoord
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#version 120
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#define INTENSITY_CORRECTION 0.6
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// normalized values for (-0.6/1.31, 0.6/1.31, 1./1.31)
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const vec3 LIGHT_TOP_DIR = vec3(-0.4574957, 0.4574957, 0.7624929);
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#define LIGHT_TOP_DIFFUSE (0.8 * INTENSITY_CORRECTION)
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#define LIGHT_TOP_SPECULAR (0.125 * INTENSITY_CORRECTION)
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#define LIGHT_TOP_SHININESS 20.0
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// normalized values for (1./1.43, 0.2/1.43, 1./1.43)
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const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
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#define LIGHT_FRONT_DIFFUSE (0.3 * INTENSITY_CORRECTION)
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#define INTENSITY_AMBIENT 0.3
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uniform vec3 uniform_color;
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// x = width, y = height
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uniform ivec2 viewport_sizes;
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uniform mat4 inv_proj_matrix;
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varying vec3 eye_center;
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float radius = 0.5;
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// x = tainted, y = specular;
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vec2 intensity;
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vec3 eye_position_from_fragment()
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{
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// Convert screen coordinates to normalized device coordinates (NDC)
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vec4 ndc = vec4(
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(gl_FragCoord.x / viewport_sizes.x - 0.5) * 2.0,
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(gl_FragCoord.y / viewport_sizes.y - 0.5) * 2.0,
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(gl_FragCoord.z - 0.5) * 2.0,
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1.0);
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// Convert NDC throuch inverse clip coordinates to view coordinates
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vec4 clip = inv_proj_matrix * ndc;
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return (clip / clip.w).xyz;
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}
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vec3 eye_position_on_sphere(vec3 eye_fragment_position)
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{
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vec3 eye_dir = normalize(eye_fragment_position);
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float a = dot(eye_dir, eye_dir);
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float b = 2.0 * dot(-eye_center, eye_dir);
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float c = dot(eye_center, eye_center) - radius * radius;
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float discriminant = b * b - 4 * a * c;
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float t = -(b + sqrt(discriminant)) / (2.0 * a);
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return t * eye_dir;
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}
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vec4 on_sphere_color(vec3 eye_on_sphere_position)
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{
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vec3 eye_normal = normalize(eye_on_sphere_position - eye_center);
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// Compute the cos of the angle between the normal and lights direction. The light is directional so the direction is constant for every vertex.
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// Since these two are normalized the cosine is the dot product. We also need to clamp the result to the [0,1] range.
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float NdotL = max(dot(eye_normal, LIGHT_TOP_DIR), 0.0);
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intensity.x = INTENSITY_AMBIENT + NdotL * LIGHT_TOP_DIFFUSE;
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intensity.y = LIGHT_TOP_SPECULAR * pow(max(dot(-normalize(eye_on_sphere_position), reflect(-LIGHT_TOP_DIR, eye_normal)), 0.0), LIGHT_TOP_SHININESS);
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// Perform the same lighting calculation for the 2nd light source (no specular applied).
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NdotL = max(dot(eye_normal, LIGHT_FRONT_DIR), 0.0);
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intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
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return vec4(vec3(intensity.y, intensity.y, intensity.y) + uniform_color.rgb * intensity.x, 1.0);
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}
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float fragment_depth(vec3 eye_pos)
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{
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vec4 clip_pos = gl_ProjectionMatrix * vec4(eye_pos, 1.0);
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float ndc_depth = clip_pos.z / clip_pos.w;
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return (((gl_DepthRange.far - gl_DepthRange.near) * ndc_depth) + gl_DepthRange.near + gl_DepthRange.far) / 2.0;
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}
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void main()
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{
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vec2 pos = gl_PointCoord - vec2(0.5);
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float sq_radius = dot(pos, pos);
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if (sq_radius > 0.25)
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discard;
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vec3 eye_on_sphere_position = eye_position_on_sphere(eye_position_from_fragment());
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gl_FragDepth = fragment_depth(eye_on_sphere_position);
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gl_FragColor = on_sphere_color(eye_on_sphere_position);
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}
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