58 lines
1.7 KiB
GLSL
58 lines
1.7 KiB
GLSL
#version 450 core
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// an attempt to test whether a geometry surface occludes the camera from a
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// light source
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layout (triangles) in;
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layout (triangle_strip, max_vertices = 4) out;
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layout (std140, binding = 0) uniform TheMat { mat4 theMat; } ;
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uniform vec3 lightPos;
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uniform vec2 camPos;
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void main()
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{
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vec3 p0 = gl_in[0].gl_Position.xyz ;
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vec3 p1 = gl_in[1].gl_Position.xyz ;
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vec3 p2 = gl_in[2].gl_Position.xyz ;
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// first determine intersection point (if any)
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vec3 u = p1 - p0 ;
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vec3 v = p2 - p0 ;
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vec3 n = cross (u,v) ;
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vec3 dir = vec3 (camPos, 100) - lightPos ;
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vec3 w0 = p0 - lightPos ;
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float a = dot(n, w0) ;
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float b = dot(n,dir) ;
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if (abs(b) < 0.00001) {}
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else {
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float r = a / b ;
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if (r < 0.0) {}
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else {
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vec3 ip = lightPos + r * dir ;
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float uu, uv, vv, wu, wv, D;
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uu = dot(u,u);
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uv = dot(u,v);
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vv = dot(v,v);
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vec3 w = ip - p0;
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wu = dot (w,u);
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wv = dot (w,v);
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D = uv * uv - uu * vv;
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//get and test parametric coords
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float s, t;
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s = (uv * wv - vv * wu) / D;
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if (s < 0.0 || s > 1.0) {}
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else
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{
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t = (uv * wu - uu * wv) / D;
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if (t < 0.0 || (s + t) > 1.0) {}
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else
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{
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gl_Position = vec4(-1,-1,50,1); EmitVertex();
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gl_Position = vec4(-1, 1,50,1); EmitVertex();
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gl_Position = vec4( 1,-1,50,1); EmitVertex();
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gl_Position = vec4( 1, 1,50,1); EmitVertex();
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EndPrimitive();
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}
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}
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}
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}
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}
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