Use a more tighly fitting quad for pointlights.

data/shaders/pointlight.vert

@@ -18,35 +18,104 @@ in vec3 Position;
 in float Energy;
 in vec3 Color;
 
-in vec2 Corner;
-
 flat out vec3 center;
 flat out float energy;
 flat out vec3 col;
 
 const float zNear = 1.;
 
-void main(void)
+// Code borrowed from https://software.intel.com/en-us/articles/deferred-rendering-for-current-and-future-rendering-pipelines
+// Maths explanations are found here http://www.gamasutra.com/view/feature/131351/the_mechanics_of_robust_stencil_.php?page=6
+
+vec2 UpdateClipRegionRoot(float nc,          /* Tangent plane x/y normal coordinate (view space) */
+                          float lc,          /* Light x/y coordinate (view space) */
+                          float lz,          /* Light z coordinate (view space) */
+                          float lightRadius,
+                          float cameraScale  /* Project scale for coordinate (_11 or _22 for x/y respectively) */)
 {
-    // Beyond that value, light is too attenuated
+    float nz = (lightRadius - nc * lc) / lz;
-    float r = 30 * Energy;
+    float pz = (lc * lc + lz * lz - lightRadius * lightRadius) /
-    center = Position;
+               (lz - (nz / nc) * lc);
-    energy = Energy;
+
-    vec4 Center = ViewMatrix * vec4(Position, 1.);
+    if (pz > 0.0f) {
-    vec4 ProjectedCornerPosition = ProjectionMatrix * (Center + r * vec4(Corner, 0., 0.));
+        float c = -nz * cameraScale / nc;
-    float adjustedDepth = ProjectedCornerPosition.z;
+        if (nc > 0.0f) // Left side boundary
-    if (Center.z > zNear) // Light is in front of the cam
+            return vec2(c, 1.);
-    {
+        else // Right side boundary
-        adjustedDepth = max(Center.z - r, zNear);
+            return vec2(-1., c);
     }
-    else if (Center.z + r > zNear) // Light is behind the cam but in range
+    return vec2(1., -1);
-    {
-        adjustedDepth = zNear;
 }
 
-    ProjectedCornerPosition /= ProjectedCornerPosition.w;
+vec2 UpdateClipRegion(float lc,          /* Light x/y coordinate (view space) */
-    ProjectedCornerPosition.zw = (ProjectionMatrix * vec4(0., 0., adjustedDepth, 1.)).zw;
+                      float lz,          /* Light z coordinate (view space) */
-    ProjectedCornerPosition.xy *= ProjectedCornerPosition.w;
+                      float lightRadius,
-    col = Color;
+                      float cameraScale  /* Project scale for coordinate (_11 or _22 for x/y respectively) */)
-    gl_Position = ProjectedCornerPosition;
+{
+    float rSq = lightRadius * lightRadius;
+    float lcSqPluslzSq = lc * lc + lz * lz;
+    float d = rSq * lc * lc - lcSqPluslzSq * (rSq - lz * lz);
+
+    if (d > 0) {
+        float a = lightRadius * lc;
+        float b = sqrt(d);
+        float nx0 = (a + b) / lcSqPluslzSq;
+        float nx1 = (a - b) / lcSqPluslzSq;
+
+        vec2 clip0 = UpdateClipRegionRoot(nx0, lc, lz, lightRadius, cameraScale);
+        vec2 clip1 = UpdateClipRegionRoot(nx1, lc, lz, lightRadius, cameraScale);
+        return vec2(max(clip0.x, clip1.x), min(clip0.y, clip1.y));
+    }
+    return vec2(1., -1.);
+}
+
+// Returns bounding box [min.x, max.x, min.y, max.y] in clip [-1, 1] space.
+vec4 ComputeClipRegion(vec3 lightPosView, float lightRadius)
+{
+    if (lightPosView.z + lightRadius >= zNear) {
+        vec2 clipX = UpdateClipRegion(lightPosView.x, lightPosView.z, lightRadius, ProjectionMatrix[0][0]);
+        vec2 clipY = UpdateClipRegion(lightPosView.y, lightPosView.z, lightRadius, ProjectionMatrix[1][1]);
+
+        return vec4(clipX, clipY);
+    }
+
+    return vec4(0.);
+}
+
+
+void main(void)
+{
+    float radius = 20. * Energy;
+    vec4 Center = ViewMatrix * vec4(Position, 1.);
+    Center /= Center.w;
+
+    vec2 ProjectedCornerPosition;
+    vec4 clip = ComputeClipRegion(Center.xyz, radius);
+    switch (gl_VertexID)
+    {
+    case 0:
+        ProjectedCornerPosition = clip.xz;
+        break;
+    case 1:
+        ProjectedCornerPosition = clip.xw;
+        break;
+    case 2:
+        ProjectedCornerPosition = clip.yz;
+        break;
+    case 3:
+        ProjectedCornerPosition = clip.yw;
+        break;
+    }
+
+    // Work out nearest depth for quad Z
+    // Clamp to near plane in case this light intersects the near plane... don't want our quad to be clipped
+    float quadDepth = max(zNear, Center.z - radius);
+
+    // Project quad depth into clip space
+    vec4 quadClip = ProjectionMatrix * vec4(0., 0., quadDepth, 1.0f);
+    gl_Position = vec4(ProjectedCornerPosition, quadClip.z / quadClip.w, 1.);
+
+    col = Color;
+    center = Position;
+    energy = Energy;
 }

src/graphics/shaders.cpp

@@ -1754,7 +1754,6 @@ namespace LightShader
     GLuint PointLightShader::attrib_Position;
     GLuint PointLightShader::attrib_Color;
     GLuint PointLightShader::attrib_Energy;
-    GLuint PointLightShader::attrib_Corner;
     GLuint PointLightShader::uniform_ntex;
     GLuint PointLightShader::uniform_dtex;
     GLuint PointLightShader::uniform_spec;
@@ -1773,7 +1772,6 @@ namespace LightShader
         attrib_Position = glGetAttribLocation(Program, "Position");
         attrib_Color = glGetAttribLocation(Program, "Color");
         attrib_Energy = glGetAttribLocation(Program, "Energy");
-        attrib_Corner = glGetAttribLocation(Program, "Corner");
         uniform_ntex = glGetUniformLocation(Program, "ntex");
         uniform_dtex = glGetUniformLocation(Program, "dtex");
         uniform_spec = glGetUniformLocation(Program, "spec");
@@ -1782,10 +1780,6 @@ namespace LightShader
         glGenVertexArrays(1, &vao);
         glBindVertexArray(vao);
 
-        glBindBuffer(GL_ARRAY_BUFFER, SharedObject::billboardvbo);
-        glEnableVertexAttribArray(attrib_Corner);
-        glVertexAttribPointer(attrib_Corner, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), 0);
-
         glGenBuffers(1, &vbo);
         glBindBuffer(GL_ARRAY_BUFFER, vbo);
         glBufferData(GL_ARRAY_BUFFER, MAXLIGHT * sizeof(PointLightInfo), 0, GL_DYNAMIC_DRAW);

src/graphics/shaders.hpp

@@ -434,7 +434,6 @@ namespace LightShader
     public:
         static GLuint Program;
         static GLuint attrib_Position, attrib_Energy, attrib_Color;
-        static GLuint attrib_Corner;
         static GLuint uniform_ntex, uniform_dtex, uniform_spec, uniform_screen;
         static GLuint vbo;
         static GLuint vao;