Workbench: Smoke: Port back Flame display

The appearance is a bit different than 2.79 where the flame was just added
on top of the smoke without correct blending.

Now it's much more realistic and using volumetric integration. You can see
the smoke actually masking the flame.

The other difference is that the flame color was not using proper color
managed blending. Now with the use of filmic it shows bright yellow.
This could be adjusted and displayed as a user parameter in the future.

1 files changed, 111 insertions, 1 deletions

diff --git a/source/blender/gpu/intern/gpu_draw.c b/source/blender/gpu/intern/gpu_draw.c
index 594a2d6d740..b7b7d8f2a35 100644
--- a/source/blender/gpu/intern/gpu_draw.c
+++ b/source/blender/gpu/intern/gpu_draw.c
@@ -63,6 +63,7 @@
 #include "IMB_imbuf_types.h"
 
 #include "BKE_bmfont.h"
+#include "BKE_colorband.h"
 #include "BKE_global.h"
 #include "BKE_image.h"
 #include "BKE_main.h"
@@ -883,6 +884,106 @@ void GPU_paint_update_image(Image *ima, ImageUser *iuser, int x, int y, int w, i
 	BKE_image_release_ibuf(ima, ibuf, NULL);
 }
 
+/* *************************** Transfer functions *************************** */
+
+enum {
+	TFUNC_FLAME_SPECTRUM = 0,
+	TFUNC_COLOR_RAMP     = 1,
+};
+
+#define TFUNC_WIDTH 256
+
+static void create_flame_spectrum_texture(float *data)
+{
+#define FIRE_THRESH 7
+#define MAX_FIRE_ALPHA 0.06f
+#define FULL_ON_FIRE 100
+
+	float *spec_pixels = MEM_mallocN(TFUNC_WIDTH * 4 * 16 * 16 * sizeof(float), "spec_pixels");
+
+	blackbody_temperature_to_rgb_table(data, TFUNC_WIDTH, 1500, 3000);
+
+	for (int i = 0; i < 16; i++) {
+		for (int j = 0; j < 16; j++) {
+			for (int k = 0; k < TFUNC_WIDTH; k++) {
+				int index = (j * TFUNC_WIDTH * 16 + i * TFUNC_WIDTH + k) * 4;
+				if (k >= FIRE_THRESH) {
+					spec_pixels[index] = (data[k * 4]);
+					spec_pixels[index + 1] = (data[k * 4 + 1]);
+					spec_pixels[index + 2] = (data[k * 4 + 2]);
+					spec_pixels[index + 3] = MAX_FIRE_ALPHA * (
+					        (k > FULL_ON_FIRE) ? 1.0f : (k - FIRE_THRESH) / ((float)FULL_ON_FIRE - FIRE_THRESH));
+				}
+				else {
+					zero_v4(&spec_pixels[index]);
+				}
+			}
+		}
+	}
+
+	memcpy(data, spec_pixels, sizeof(float) * 4 * TFUNC_WIDTH);
+
+	MEM_freeN(spec_pixels);
+
+#undef FIRE_THRESH
+#undef MAX_FIRE_ALPHA
+#undef FULL_ON_FIRE
+}
+
+static void create_color_ramp(const ColorBand *coba, float *data)
+{
+	for (int i = 0; i < TFUNC_WIDTH; i++) {
+		BKE_colorband_evaluate(coba, (float)i / TFUNC_WIDTH, &data[i * 4]);
+	}
+}
+
+static GPUTexture *create_transfer_function(int type, const ColorBand *coba)
+{
+	float *data = MEM_mallocN(sizeof(float) * 4 * TFUNC_WIDTH, __func__);
+
+	switch (type) {
+		case TFUNC_FLAME_SPECTRUM:
+			create_flame_spectrum_texture(data);
+			break;
+		case TFUNC_COLOR_RAMP:
+			create_color_ramp(coba, data);
+			break;
+	}
+
+	GPUTexture *tex = GPU_texture_create_1D(TFUNC_WIDTH, GPU_RGBA8, data, NULL);
+
+	MEM_freeN(data);
+
+	return tex;
+}
+
+static GPUTexture *create_field_texture(SmokeDomainSettings *sds)
+{
+	float *field = NULL;
+
+	switch (sds->coba_field) {
+#ifdef WITH_SMOKE
+		case FLUID_FIELD_DENSITY:    field = smoke_get_density(sds->fluid); break;
+		case FLUID_FIELD_HEAT:       field = smoke_get_heat(sds->fluid); break;
+		case FLUID_FIELD_FUEL:       field = smoke_get_fuel(sds->fluid); break;
+		case FLUID_FIELD_REACT:      field = smoke_get_react(sds->fluid); break;
+		case FLUID_FIELD_FLAME:      field = smoke_get_flame(sds->fluid); break;
+		case FLUID_FIELD_VELOCITY_X: field = smoke_get_velocity_x(sds->fluid); break;
+		case FLUID_FIELD_VELOCITY_Y: field = smoke_get_velocity_y(sds->fluid); break;
+		case FLUID_FIELD_VELOCITY_Z: field = smoke_get_velocity_z(sds->fluid); break;
+		case FLUID_FIELD_COLOR_R:    field = smoke_get_color_r(sds->fluid); break;
+		case FLUID_FIELD_COLOR_G:    field = smoke_get_color_g(sds->fluid); break;
+		case FLUID_FIELD_COLOR_B:    field = smoke_get_color_b(sds->fluid); break;
+		case FLUID_FIELD_FORCE_X:    field = smoke_get_force_x(sds->fluid); break;
+		case FLUID_FIELD_FORCE_Y:    field = smoke_get_force_y(sds->fluid); break;
+		case FLUID_FIELD_FORCE_Z:    field = smoke_get_force_z(sds->fluid); break;
+#endif
+		default: return NULL;
+	}
+
+	return GPU_texture_create_3D(sds->res[0], sds->res[1], sds->res[2], GPU_R8, field, NULL);
+}
+
 void GPU_free_smoke(SmokeModifierData *smd)
 {
 	if (smd->type & MOD_SMOKE_TYPE_DOMAIN && smd->domain) {
@@ -897,6 +998,10 @@ void GPU_free_smoke(SmokeModifierData *smd)
 		if (smd->domain->tex_flame)
 			GPU_texture_free(smd->domain->tex_flame);
 		smd->domain->tex_flame = NULL;
+
+		if (smd->domain->tex_flame_coba)
+			GPU_texture_free(smd->domain->tex_flame_coba);
+		smd->domain->tex_flame_coba = NULL;
 	}
 }
 
@@ -966,12 +1071,16 @@ void GPU_create_smoke(SmokeModifierData *smd, int highres)
 			sds->tex_flame = (
 			        smoke_turbulence_has_fuel(sds->wt) ?
 			                GPU_texture_create_nD(
-			                        sds->res[0], sds->res[1], sds->res[2], 3,
+			                        sds->res_wt[0], sds->res_wt[1], sds->res_wt[2], 3,
 			                        smoke_turbulence_get_flame(sds->wt),
 			                        GPU_R8, GPU_DATA_FLOAT, 0, true, NULL) :
 			                NULL);
 		}
 
+		if (sds->tex_flame) {
+			sds->tex_flame_coba = create_transfer_function(TFUNC_FLAME_SPECTRUM, NULL);
+		}
+
 		sds->tex_shadow = GPU_texture_create_nD(
 		                      sds->res[0], sds->res[1], sds->res[2], 3,
 		                      sds->shadow,
@@ -982,6 +1091,7 @@ void GPU_create_smoke(SmokeModifierData *smd, int highres)
 	(void)highres;
 	smd->domain->tex = NULL;
 	smd->domain->tex_flame = NULL;
+	smd->domain->tex_flame_coba = NULL;
 	smd->domain->tex_shadow = NULL;
 #endif // WITH_SMOKE
 }