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1 #version 410 compatibility
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2
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3 layout(quads, ccw) in;
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4
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5 out vec3 normal;
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6 out vec3 vpos;
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7
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8 uniform vec3 norm_scale;
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9
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10 vec3 bezier_patch(float u, float v);
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11 vec3 bezier_patch_norm(float u, float v);
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12 float bernstein(int i, float x);
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13
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14 void main()
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15 {
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16 vec3 pos = bezier_patch(gl_TessCoord.x, gl_TessCoord.y);
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17 normal = gl_NormalMatrix * bezier_patch_norm(gl_TessCoord.x, gl_TessCoord.y);
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18
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19 gl_Position = gl_ModelViewProjectionMatrix * vec4(pos, 1.0);
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20 vpos = (gl_ModelViewMatrix * vec4(pos, 1.0)).xyz;
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21 }
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22
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23 vec3 bezier_patch(float u, float v)
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24 {
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25 int i, j;
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26 vec3 res = vec3(0.0, 0.0, 0.0);
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27
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28 for(j=0; j<4; j++) {
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29 for(i=0; i<4; i++) {
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30 float bu = bernstein(i, u);
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31 float bv = bernstein(j, v);
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32
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33 res += gl_in[j * 4 + i].gl_Position.xyz * bu * bv;
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34 }
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35 }
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36 return res;
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37 }
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38
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39 #define DT 0.0001
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40 vec3 bezier_patch_norm(float u, float v)
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41 {
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42 vec3 tang = bezier_patch(u + DT, v) - bezier_patch(u - DT, v);
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43 vec3 bitan = bezier_patch(u, v + DT) - bezier_patch(u, v - DT);
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44 return cross(tang, bitan) * norm_scale;
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45 }
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46
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47 float bernstein(int i, float x)
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48 {
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49 float invx = 1.0 - x;
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50
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51 if(i == 0) {
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52 return invx * invx * invx;
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53 }
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54 if(i == 1) {
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55 return 3 * x * invx * invx;
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56 }
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57 if(i == 2) {
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58 return 3 * x * x * invx;
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59 }
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60 return x * x * x;
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61 }
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