Commit: 77062e8bbb09049ac76d210bacb9b0945bad783e
Author: Brecht Van Lommel
Date:   Fri Feb 23 04:55:54 2018 +0100
Branches: blender2.8
https://developer.blender.org/rB77062e8bbb09049ac76d210bacb9b0945bad783e

Eevee: add blackbody shader node support.

This replaces the blackbody to RGB code with the simpler and faster one from
Cycles. It's a little different but the other placing using this is the legacy
volume drawing, so no need to stay compatible with that.

===================================================================

M       source/blender/blenlib/intern/math_color.c
M       source/blender/gpu/shaders/gpu_shader_material.glsl
M       source/blender/nodes/shader/nodes/node_shader_blackbody.c

===================================================================

diff --git a/source/blender/blenlib/intern/math_color.c 
b/source/blender/blenlib/intern/math_color.c
index cb39134af45..534abeb913d 100644
--- a/source/blender/blenlib/intern/math_color.c
+++ b/source/blender/blenlib/intern/math_color.c
@@ -656,135 +656,80 @@ void rgb_to_lab(float r, float g, float b, float *ll, 
float *la, float *lb)
        xyz_to_lab(x, y, z, ll, la, lb);
 }
 
-static void xyz_to_lms(float x, float y, float z, float *l, float *m, float *s)
-{
-       *l =  0.3897f * x + 0.6890f * y - 0.0787f * z;
-       *m = -0.2298f * x + 1.1834f * y + 0.0464f * z;
-       *s = z;
-}
-
-static void lms_to_xyz(float l, float m, float s, float *x, float *y, float *z)
-{
-       *x =  1.9102f * l - 1.1121f * m + 0.2019f * s;
-       *y =  0.3709f * l + 0.6290f * m + 0.0000f * s;
-       *z = s;
-}
-
-static void normalize_rgb(float rgb[3])
-{
-       const float max = max_fff(rgb[0], rgb[1], rgb[2]);
+/* ****************************** blackbody ******************************** */
 
-       if (max > 0.0f) {
-               mul_v3_fl(rgb, 1.0f / max);
-       }
-}
-
-/* Color rendering of spectra, adapted from public domain code by John Walker,
- * http://www.fourmilab.ch/
+/* Calculate color in range 800..12000 using an approximation
+ * a/x+bx+c for R and G and ((at + b)t + c)t + d) for B
+ * Max absolute error for RGB is (0.00095, 0.00077, 0.00057),
+ * which is enough to get the same 8 bit/channel color.
  */
 
-static void spectrum_to_xyz(float temperature, float xyz[3])
-{
-       int i;
-       float lambda, x = 0.0f, y = 0.0f, z = 0.0f, xyz_sum;
-
-       /* CIE colour matching functions xBar, yBar, and zBar for wavelengths 
from
-        * 380 through 780 nanometers, every 5 nanometers.
-        * For a wavelength lambda in this range:
-        *
-        * cie_colour_match[(lambda - 380) / 5][0] = xBar
-        * cie_colour_match[(lambda - 380) / 5][1] = yBar
-        * cie_colour_match[(lambda - 380) / 5][2] = zBar
-        */
-
-       const float cie_colour_match[81][3] = {
-           {0.0014f, 0.0000f, 0.0065f}, {0.0022f, 0.0001f, 0.0105f}, {0.0042f, 
0.0001f, 0.0201f},
-           {0.0076f, 0.0002f, 0.0362f}, {0.0143f, 0.0004f, 0.0679f}, {0.0232f, 
0.0006f, 0.1102f},
-           {0.0435f, 0.0012f, 0.2074f}, {0.0776f, 0.0022f, 0.3713f}, {0.1344f, 
0.0040f, 0.6456f},
-           {0.2148f, 0.0073f, 1.0391f}, {0.2839f, 0.0116f, 1.3856f}, {0.3285f, 
0.0168f, 1.6230f},
-           {0.3483f, 0.0230f, 1.7471f}, {0.3481f, 0.0298f, 1.7826f}, {0.3362f, 
0.0380f, 1.7721f},
-           {0.3187f, 0.0480f, 1.7441f}, {0.2908f, 0.0600f, 1.6692f}, {0.2511f, 
0.0739f, 1.5281f},
-           {0.1954f, 0.0910f, 1.2876f}, {0.1421f, 0.1126f, 1.0419f}, {0.0956f, 
0.1390f, 0.8130f},
-           {0.0580f, 0.1693f, 0.6162f}, {0.0320f, 0.2080f, 0.4652f}, {0.0147f, 
0.2586f, 0.3533f},
-           {0.0049f, 0.3230f, 0.2720f}, {0.0024f, 0.4073f, 0.2123f}, {0.0093f, 
0.5030f, 0.1582f},
-           {0.0291f, 0.6082f, 0.1117f}, {0.0633f, 0.7100f, 0.0782f}, {0.1096f, 
0.7932f, 0.0573f},
-           {0.1655f, 0.8620f, 0.0422f}, {0.2257f, 0.9149f, 0.0298f}, {0.2904f, 
0.9540f, 0.0203f},
-           {0.3597f, 0.9803f, 0.0134f}, {0.4334f, 0.9950f, 0.0087f}, {0.5121f, 
1.0000f, 0.0057f},
-           {0.5945f, 0.9950f, 0.0039f}, {0.6784f, 0.9786f, 0.0027f}, {0.7621f, 
0.9520f, 0.0021f},
-           {0.8425f, 0.9154f, 0.0018f}, {0.9163f, 0.8700f, 0.0017f}, {0.9786f, 
0.8163f, 0.0014f},
-           {1.0263f, 0.7570f, 0.0011f}, {1.0567f, 0.6949f, 0.0010f}, {1.0622f, 
0.6310f, 0.0008f},
-           {1.0456f, 0.5668f, 0.0006f}, {1.0026f, 0.5030f, 0.0003f}, {0.9384f, 
0.4412f, 0.0002f},
-           {0.8544f, 0.3810f, 0.0002f}, {0.7514f, 0.3210f, 0.0001f}, {0.6424f, 
0.2650f, 0.0000f},
-           {0.5419f, 0.2170f, 0.0000f}, {0.4479f, 0.1750f, 0.0000f}, {0.3608f, 
0.1382f, 0.0000f},
-           {0.2835f, 0.1070f, 0.0000f}, {0.2187f, 0.0816f, 0.0000f}, {0.1649f, 
0.0610f, 0.0000f},
-           {0.1212f, 0.0446f, 0.0000f}, {0.0874f, 0.0320f, 0.0000f}, {0.0636f, 
0.0232f, 0.0000f},
-           {0.0468f, 0.0170f, 0.0000f}, {0.0329f, 0.0119f, 0.0000f}, {0.0227f, 
0.0082f, 0.0000f},
-           {0.0158f, 0.0057f, 0.0000f}, {0.0114f, 0.0041f, 0.0000f}, {0.0081f, 
0.0029f, 0.0000f},
-           {0.0058f, 0.0021f, 0.0000f}, {0.0041f, 0.0015f, 0.0000f}, {0.0029f, 
0.0010f, 0.0000f},
-           {0.0020f, 0.0007f, 0.0000f}, {0.0014f, 0.0005f, 0.0000f}, {0.0010f, 
0.0004f, 0.0000f},
-           {0.0007f, 0.0002f, 0.0000f}, {0.0005f, 0.0002f, 0.0000f}, {0.0003f, 
0.0001f, 0.0000f},
-           {0.0002f, 0.0001f, 0.0000f}, {0.0002f, 0.0001f, 0.0000f}, {0.0001f, 
0.0000f, 0.0000f},
-           {0.0001f, 0.0000f, 0.0000f}, {0.0001f, 0.0000f, 0.0000f}, {0.0000f, 
0.0000f, 0.0000f}
-       };
-
-       for (i = 0, lambda = 380.0f; lambda < 780.1f; i++, lambda += 5.0f) {
-               /* wavelength in meter */
-               const float wlm = lambda * 1e-9f;
-               const float Me = (3.74183e-16f * powf(wlm, -5.0f)) / 
(expf(1.4388e-2f / (wlm * temperature)) - 1.0f);
-
-               x += Me * cie_colour_match[i][0];
-               y += Me * cie_colour_match[i][1];
-               z += Me * cie_colour_match[i][2];
+static const float blackbody_table_r[6][3] = {
+       {  2.52432244e+03f, -1.06185848e-03f, 3.11067539e+00f },
+       {  3.37763626e+03f, -4.34581697e-04f, 1.64843306e+00f },
+       {  4.10671449e+03f, -8.61949938e-05f, 6.41423749e-01f },
+       {  4.66849800e+03f,  2.85655028e-05f, 1.29075375e-01f },
+       {  4.60124770e+03f,  2.89727618e-05f, 1.48001316e-01f },
+       {  3.78765709e+03f,  9.36026367e-06f, 3.98995841e-01f },
+};
+
+static const float blackbody_table_g[6][3] = {
+       { -7.50343014e+02f,  3.15679613e-04f, 4.73464526e-01f },
+       { -1.00402363e+03f,  1.29189794e-04f, 9.08181524e-01f },
+       { -1.22075471e+03f,  2.56245413e-05f, 1.20753416e+00f },
+       { -1.42546105e+03f, -4.01730887e-05f, 1.44002695e+00f },
+       { -1.18134453e+03f, -2.18913373e-05f, 1.30656109e+00f },
+       { -5.00279505e+02f, -4.59745390e-06f, 1.09090465e+00f },
+};
+
+static const float blackbody_table_b[6][4] = {
+       { 0.0f, 0.0f, 0.0f, 0.0f },
+       { 0.0f, 0.0f, 0.0f, 0.0f },
+       { 0.0f, 0.0f, 0.0f, 0.0f },
+       { -2.02524603e-11f,  1.79435860e-07f, -2.60561875e-04f, 
-1.41761141e-02f },
+       { -2.22463426e-13f, -1.55078698e-08f,  3.81675160e-04f, 
-7.30646033e-01f },
+       {  6.72595954e-13f, -2.73059993e-08f,  4.24068546e-04f, 
-7.52204323e-01f },
+};
+
+static void blackbody_temperature_to_rgb(float rgb[3], float t)
+{
+       if(t >= 12000.0f) {
+               rgb[0] = 0.826270103f;
+               rgb[1] = 0.994478524f;
+               rgb[2] = 1.56626022f;
+       }
+       else if(t < 965.0f) {
+               rgb[0] = 4.70366907f;
+               rgb[1] = 0.0f;
+               rgb[2] = 0.0f;
+       }
+       else {
+               int i = (t >= 6365.0f)? 5:
+                       (t >= 3315.0f)? 4:
+                       (t >= 1902.0f)? 3:
+                       (t >= 1449.0f)? 2:
+                       (t >= 1167.0f)? 1: 0;
+
+               const float *r = blackbody_table_r[i];
+               const float *g = blackbody_table_g[i];
+               const float *b = blackbody_table_b[i];
+
+               const float t_inv = 1.0f / t;
+               rgb[0] = r[0] * t_inv + r[1] * t + r[2];
+               rgb[1] = g[0] * t_inv + g[1] * t + g[2];
+               rgb[2] = ((b[0] * t + b[1]) * t + b[2]) * t + b[3];
        }
-
-       xyz_sum = (x + y + z);
-
-       xyz[0] = x / xyz_sum;
-       xyz[1] = y / xyz_sum;
-       xyz[2] = z / xyz_sum;
 }
 
 void blackbody_temperature_to_rgb_table(float *r_table, int width, float min, 
float max)
 {
-       int i, j = 0, dj = 1;
-       float rgb[3], xyz[3], lms[3], lms_w[3];
-       float bb_temp;
-
-       if (min < max) {
-               SWAP(float, min, max);
-               j = width - 1;
-               dj = -1;
-       }
+       for (int i = 0; i < width; i++) {
+               float temperature = min + (max - min) / (float)width * (float)i;
 
-       for (i = 0; i < width; i++, j += dj) {
-               bb_temp = min + (max - min) / (float)width * (float)i;
+               float rgb[3];
+               blackbody_temperature_to_rgb(rgb, temperature);
 
-               /* integrate blackbody radiation spectrum to XYZ */
-               spectrum_to_xyz(bb_temp, xyz);
-
-               /* normalize highest temperature to white (in LMS system) */
-               xyz_to_lms(xyz[0], xyz[1], xyz[2], &lms[0], &lms[1], &lms[2]);
-
-               if (i == 0) {
-                       lms_w[0] = 1.0f / lms[0];
-                       lms_w[1] = 1.0f / lms[1];
-                       lms_w[2] = 1.0f / lms[2];
-               }
-
-               mul_v3_v3(lms, lms_w);
-
-               lms_to_xyz(lms[0], lms[1], lms[2], &xyz[0], &xyz[1], &xyz[2]);
-
-               /* convert to RGB */
-               xyz_to_rgb(xyz[0], xyz[1], xyz[2], &rgb[0], &rgb[1], &rgb[2], 
BLI_XYZ_CIE);
-               constrain_rgb(&rgb[0], &rgb[1], &rgb[2]);
-               normalize_rgb(rgb);
-
-               copy_v3_v3(&r_table[(j << 2)], rgb);
-
-               if (rgb[2] > 0.1f)
-                       r_table[(j << 2) + 3] = rgb[2];
-               else
-                       r_table[(j << 2) + 3] = 0.0f;
+               copy_v3_v3(&r_table[i * 4], rgb);
+               r_table[i * 4 + 3] = 0.0f;
        }
 }
diff --git a/source/blender/gpu/shaders/gpu_shader_material.glsl 
b/source/blender/gpu/shaders/gpu_shader_material.glsl
index 71333149634..8d120ae8984 100644
--- a/source/blender/gpu/shaders/gpu_shader_material.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_material.glsl
@@ -3075,6 +3075,20 @@ void node_volume_absorption(vec4 color, float density, 
out Closure result)
 #endif
 }
 
+void node_blackbody(float temperature, sampler2D spectrummap, out vec4 color)
+{
+    if(temperature >= 12000.0) {
+        color = vec4(0.826270103, 0.994478524, 1.56626022, 1.0);
+    }
+    else if(temperature < 965.0) {
+        color = vec4(4.70366907, 0.0, 0.0, 1.0);
+    }
+       else {
+               float t = (temperature - 965.0) / (12000.0 - 965.0);
+               color = vec4(texture(spectrummap, vec2(t, 0.0)).rgb, 1.0);
+       }
+}
+
 /* closures */
 
 void node_mix_shader(float fac, Closure shader1, Closure shader2, out Closure 
shader)
diff --git a/source/blender/nodes/shader/nodes/node_shader_blackbody.c 
b/source/blender/nodes/shader/nodes/node_shader_blackbody.c
index af89a959554..28019651926 100644
--- a/source/blender/nodes/shader/nodes/node_shader_blackbody.c
+++ b/source/blender/nodes/shader/nodes/node_shader_blackbody.c
@@ -38,6 +38,16 @@ static bNodeSocketTemplate sh_node_blackbody_out[] = {
        {       -1, 0, ""       }
 };
 
+static int node_shader_gpu_blackbody(GPUMaterial *mat, bNode *node, 
bNodeExecData *UNUSED(execdata), GPUNodeStack *in, GPUNodeStack *out)
+{
+       const int size = 256;
+       float *data = MEM_mallocN(sizeof(float) * size * 4, "blackbody 
texture");
+
+       blackbody_temperature_to_rgb_table(data, size, 965.0f, 12000.0f);
+
+       return GPU_stack_link(mat, node, "node_blackbody", in, out, 
GPU_texture(size, data));
+}
+
 /* node type definition */
 void register_node_type_sh_blackbody(void)
 {
@@ -49,6 +59,7 @@ void register_node_type_sh_blackbody(void)
        node_type_socket_templates(&ntype, sh_node_blackbody_in, 
sh_node_blackbody_out);
        node_type_init(&ntype, NULL);
        node_type_storage(&ntype, "", NULL, NULL);
+       node_type_gpu(&ntype, node_shader_gpu_blackbody);
 
        nodeRegisterType(&ntype);
 }

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