Annotation of /trunk/test/vr-curv-quad.diderot

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Revision 1124 - (view) (download)

1 :	jhr	1115	// vr-curv
2 :			//
3 :			// Demonstration of curvature-based transfer functions in volume rendering
4 :			//
5 :			// process output with:
6 :			// unu reshape -i mip.txt -s 4 480 345 | overrgb -i - -b 0.1 0.15 0.2 -g 1.2 -o - | unu quantize -b 8 -min 0 -max 255 -o vr-curv-quad.png
7 :
8 :			field#2(3)[] F = bspln3 ⊛ load("../data/quad-patches-pad.nrrd");
9 :			field#0(2)[3] RGB = tent ⊛ load("../data/txf/2d-bow.nrrd");
10 :
11 :			// set camera, image, and rendering parameters
12 :			vec3 camEye = [183.021, -411.857, 686.458];
13 :			vec3 camAt = [55.4037, 40.2407, 4.32732];
14 :			vec3 camUp = [0.0, 0.0, 1.0];
15 :			real camNear = -42.0;
16 :			real camFar = 42.0;
17 :			real camFOV = 7.15;
18 :			int imgResU = 480;
19 :			int imgResV = 345;
20 :			real rayStep = 0.2;
21 :			real valOpacMin = -0.25;
22 :			real valOpacMax = -0.10;
23 :			vec3 lightVspDir = [0.9, -2.5, -2.5];
24 :			vec3 lightRGB = [1.0, 1.0, 1.0];
25 :			real phongKa = 0.1;
26 :			real phongKd = 0.7;
27 :			real phongKs = 0.3;
28 :			real phongSp = 45.0;
29 :
30 :			// (boilerplate) computation of camera and light info
31 :			real camDist = |camAt - camEye|;
32 :			real camVspNear = camNear + camDist;
33 :			real camVspFar = camFar + camDist;
34 :			vec3 camN = normalize(camAt - camEye);
35 :			vec3 camU = normalize(camN × camUp);
36 :			vec3 camV = camN × camU;
37 :			real camVmax = tan(camFOV*π/360.0)*camDist;
38 :			real camUmax = camVmax*real(imgResU)/real(imgResV);
39 :			vec3 lightDir = normalize(lightVspDir[0]*camU +
40 :			lightVspDir[1]*camV +
41 :			lightVspDir[2]*camN);
42 :
43 :			strand RayCast (int ui, int vi) {
44 :			real rayU = lerp(-camUmax, camUmax, -0.5, real(ui), real(imgResU)-0.5);
45 :			real rayV = lerp(-camVmax, camVmax, -0.5, real(vi), real(imgResV)-0.5);
46 :			vec3 rayVec = (camDist*camN + rayU*camU + rayV*camV)/camDist;
47 :	glk	1124	vec3 vv = normalize(-rayVec);
48 :	jhr	1115
49 :			real rayN = camVspNear;
50 :			real rayTransp = 1.0;
51 :			vec3 rayRGB = [0.0, 0.0, 0.0];
52 :			output vec4 outRGBA = [0.0, 0.0, 0.0, 0.0];
53 :
54 :			update {
55 :			vec3 pos = camEye + rayN*rayVec;
56 :			if (inside (pos,F)) {
57 :			real val = F(pos);
58 :			if (val > valOpacMin) { // we have some opacity
59 :			vec3 grad = -∇F(pos);
60 :			vec3 norm = normalize(grad);
61 :			// begin curvature computation
62 :			tensor[3,3] H = ∇(∇F)(pos);
63 :			tensor[3,3] P = identity[3] - norm⊗norm;
64 :			tensor[3,3] G = -(P•H•P)/|grad|;
65 :			real disc = max(0.0, sqrt(2.0*|G|^2 - trace(G)^2));
66 :			real k1 = (trace(G) + disc)/2.0;
67 :			real k2 = (trace(G) - disc)/2.0;
68 :			// finished curvature computation; begin finding sample RGBA
69 :	glk	1124	k1 = max(-1.0, min(1.0, 6.0*k1));
70 :			k2 = max(-1.0, min(1.0, 6.0*k2));
71 :	jhr	1115	vec3 matRGB = RGB([k1,k2]);
72 :			real alpha = min(1.0, lerp(0.0, 1.0,
73 :			valOpacMin, val, valOpacMax));
74 :			real ld = max(0.0, norm • lightDir);
75 :	glk	1124	real hd = max(0.0, norm • normalize(lightDir + vv));
76 :	jhr	1115	// Phong shading
77 :			vec3 pntRGB = (phongKa*matRGB
78 :			+ phongKd*ld*modulate(matRGB, lightRGB)
79 :			+ phongKs*hd^phongSp*lightRGB);
80 :			// composite with existing ray color and transparency
81 :			rayRGB = rayRGB + rayTransp*alpha*pntRGB;
82 :			rayTransp = rayTransp*(1.0 - alpha);
83 :			}
84 :			}
85 :			if (rayTransp < 0.01) { // early ray termination
86 :			rayTransp = 0.0;
87 :			outRGBA = [rayRGB[0], rayRGB[1], rayRGB[2], 1.0 - rayTransp];
88 :			stabilize;
89 :			}
90 :			if (rayN > camVspFar) {
91 :			outRGBA = [rayRGB[0], rayRGB[1], rayRGB[2], 1.0 - rayTransp];
92 :			stabilize;
93 :			}
94 :			rayN = rayN + rayStep;
95 :			}
96 :
97 :			/* render: output maxval */
98 :			}
99 :
100 :			initially [ RayCast(ui, vi) | vi in 0..(imgResV-1), ui in 0..(imgResU-1) ];

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