109 lines
3.6 KiB
GLSL
109 lines
3.6 KiB
GLSL
in vec3 Position;
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in float Energy;
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in vec3 Color;
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in float Radius;
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flat out vec3 center;
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flat out float energy;
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flat out vec3 col;
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flat out float radius;
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const float zNear = 1.;
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// Code borrowed from https://software.intel.com/en-us/articles/deferred-rendering-for-current-and-future-rendering-pipelines
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// Maths explanations are found here http://www.gamasutra.com/view/feature/131351/the_mechanics_of_robust_stencil_.php?page=6
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vec2 UpdateClipRegionRoot(float nc, /* Tangent plane x/y normal coordinate (view space) */
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float lc, /* Light x/y coordinate (view space) */
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float lz, /* Light z coordinate (view space) */
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float lightRadius,
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float cameraScale /* Project scale for coordinate (_11 or _22 for x/y respectively) */)
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{
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float nz = (lightRadius - nc * lc) / lz;
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float pz = (lc * lc + lz * lz - lightRadius * lightRadius) /
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(lz - (nz / nc) * lc);
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if (pz > 0.) {
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float c = -nz * cameraScale / nc;
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if (nc > 0.) // Left side boundary
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return vec2(c, 1.);
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else // Right side boundary
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return vec2(-1., c);
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}
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return vec2(-1., 1.);
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}
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vec2 UpdateClipRegion(float lc, /* Light x/y coordinate (view space) */
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float lz, /* Light z coordinate (view space) */
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float lightRadius,
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float cameraScale /* Project scale for coordinate (_11 or _22 for x/y respectively) */)
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{
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float rSq = lightRadius * lightRadius;
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float lcSqPluslzSq = lc * lc + lz * lz;
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float d = rSq * lc * lc - lcSqPluslzSq * (rSq - lz * lz);
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// The camera is inside lignt bounding sphere, quad fits whole screen
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if (d <= 0.)
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return vec2(-1., 1.);
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float a = lightRadius * lc;
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float b = sqrt(d);
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float nx0 = (a + b) / lcSqPluslzSq;
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float nx1 = (a - b) / lcSqPluslzSq;
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vec2 clip0 = UpdateClipRegionRoot(nx0, lc, lz, lightRadius, cameraScale);
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vec2 clip1 = UpdateClipRegionRoot(nx1, lc, lz, lightRadius, cameraScale);
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return vec2(max(clip0.x, clip1.x), min(clip0.y, clip1.y));
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}
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// Returns bounding box [min.x, max.x, min.y, max.y] in clip [-1, 1] space.
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vec4 ComputeClipRegion(vec3 lightPosView, float lightRadius)
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{
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if (lightPosView.z + lightRadius >= zNear) {
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vec2 clipX = UpdateClipRegion(lightPosView.x, lightPosView.z, lightRadius, ProjectionMatrix[0][0]);
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vec2 clipY = UpdateClipRegion(lightPosView.y, lightPosView.z, lightRadius, ProjectionMatrix[1][1]);
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return vec4(clipX, clipY);
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}
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return vec4(0.);
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}
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void main(void)
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{
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vec4 Center = ViewMatrix * vec4(Position, 1.);
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Center /= Center.w;
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vec2 ProjectedCornerPosition;
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vec4 clip = ComputeClipRegion(Center.xyz, Radius);
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switch (gl_VertexID)
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{
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case 0:
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ProjectedCornerPosition = clip.xz;
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break;
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case 1:
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ProjectedCornerPosition = clip.xw;
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break;
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case 2:
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ProjectedCornerPosition = clip.yz;
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break;
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case 3:
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ProjectedCornerPosition = clip.yw;
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break;
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}
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// Work out nearest depth for quad Z
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// Clamp to near plane in case this light intersects the near plane... don't want our quad to be clipped
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float quadDepth = max(zNear, Center.z - Radius);
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// Project quad depth into clip space
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vec4 quadClip = ProjectionMatrix * vec4(0., 0., quadDepth, 1.0f);
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gl_Position = vec4(ProjectedCornerPosition, quadClip.z / quadClip.w, 1.);
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col = Color;
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center = Position;
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energy = Energy;
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radius = Radius;
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}
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