43 lines
1.3 KiB
Text
43 lines
1.3 KiB
Text
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#version 150 compatibility
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// bump map texture
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uniform sampler2D bump_map;
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// bump map texture resolution
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uniform int bump_map_res;
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// scaling of height function
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uniform float bump_scale;
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vec3 bump_map_normal(vec3 s, vec2 tc, vec3 N)
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{
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// lookup height value
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float h_0 = texture2D(bump_map,tc).x;
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// derivatives in image space
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mat2 tc_i = mat2(dFdx(tc),dFdy(tc));
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vec2 h_i = vec2(texture2D(bump_map,tc+tc_i[0]).x - h_0,
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texture2D(bump_map,tc+tc_i[1]).x - h_0);
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vec3 s_x = dFdx(s);
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vec3 s_y = dFdy(s);
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// compute T_i^(-1)
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float det_tc_i = tc_i[0][0]*tc_i[1][1] - tc_i[1][0]*tc_i[0][1];
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mat2 i_tc = mat2(tc_i[1][1], -tc_i[1][0],
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-tc_i[0][1], tc_i[0][0])/det_tc_i;
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// transform derivatives to texture space
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vec2 h_tc = i_tc*h_i;
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vec2 s_tc0 = i_tc * vec2(s_x[0],s_y[0]);
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vec2 s_tc1 = i_tc * vec2(s_x[1],s_y[1]);
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vec2 s_tc2 = i_tc * vec2(s_x[2],s_y[2]);
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vec3 s_u = vec3(s_tc0.x,s_tc1.x,s_tc2.x);
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vec3 s_v = vec3(s_tc0.y,s_tc1.y,s_tc2.y);
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// compute scaling factor for original normal
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float f = length(cross(s_u,s_v));
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// compute bump mapped normal
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vec3 n = normalize(N);
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float height_scale = bump_scale / float(bump_map_res);
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n = f*n + cross(height_scale*(h_tc[1]*s_u-h_tc[0]*s_v),n);
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return normalize(n);
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}
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