15 lines
776 B
GLSL
15 lines
776 B
GLSL
// Sun Most Representative Point (used for MRP area lighting method)
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// From "Frostbite going PBR" paper
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vec3 sunDirection(vec3 R, vec3 sun_direction, float sun_angle_tan_half, mat4 inverse_view_matrix)
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{
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sun_direction = normalize((transpose(inverse_view_matrix) * vec4(sun_direction, 0.)).xyz);
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float DdotR = dot(sun_direction, R);
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vec3 S = normalize(R - DdotR * sun_direction);
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float sun_angle_tan_half2 = 1 + sun_angle_tan_half * sun_angle_tan_half;
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vec2 sun_angle_sin_cos = vec2(2 * sun_angle_tan_half, 2 - sun_angle_tan_half2) / sun_angle_tan_half2;
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// Equivalent to DdotR < cos(sun_angle)
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float factor = step(DdotR, sun_angle_sin_cos.y);
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return mix(R, normalize(sun_direction * sun_angle_sin_cos.y + S * sun_angle_sin_cos.x), factor);
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}
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