Implement particle velocity and acceleration visualization

source/blender/draw/intern/draw_cache_impl_particles.c

@@ -272,7 +272,7 @@ static void particle_batch_cache_ensure_pos(ParticleSystem *psys, ParticleBatchC
 {
 	if (cache->pos == NULL) {
 		static VertexFormat format = { 0 };
-		static unsigned pos_id, rot_id;
+		static unsigned pos_id, rot_id, val_id;
 		int i, curr_point;
 		ParticleData *pa;
 
@@ -283,6 +283,7 @@ static void particle_batch_cache_ensure_pos(ParticleSystem *psys, ParticleBatchC
 			/* initialize vertex format */
 			pos_id = VertexFormat_add_attrib(&format, "pos", COMP_F32, 3, KEEP_FLOAT);
 			rot_id = VertexFormat_add_attrib(&format, "rot", COMP_F32, 4, KEEP_FLOAT);
+			val_id = VertexFormat_add_attrib(&format, "val", COMP_F32, 1, KEEP_FLOAT);
 		}
 
 		cache->pos = VertexBuffer_create_with_format(&format);
@@ -292,9 +293,25 @@ static void particle_batch_cache_ensure_pos(ParticleSystem *psys, ParticleBatchC
 			if (pa->state.time >= pa->time && pa->state.time < pa->dietime &&
 			    !(pa->flag & (PARS_NO_DISP | PARS_UNEXIST)))
 			{
+				float val;
+
 				VertexBuffer_set_attrib(cache->pos, pos_id, curr_point, pa->state.co);
 				VertexBuffer_set_attrib(cache->pos, rot_id, curr_point, pa->state.rot);
 
+				switch (psys->part->draw_col) {
+					case PART_DRAW_COL_VEL:
+						val = len_v3(pa->state.vel) / psys->part->color_vec_max;
+						break;
+					case PART_DRAW_COL_ACC:
+						val = len_v3v3(pa->state.vel, pa->prev_state.vel) / ((pa->state.time - pa->prev_state.time) * psys->part->color_vec_max);
+						break;
+					default:
+						val = -1.0f;
+						break;
+				}
+
+				VertexBuffer_set_attrib(cache->pos, val_id, curr_point, &val);
+
 				curr_point++;
 			}
 		}

source/blender/draw/intern/draw_common.c

@@ -26,10 +26,12 @@
 #include "DRW_render.h"
 
 #include "GPU_shader.h"
+#include "GPU_texture.h"
 
 #include "UI_resources.h"
 
 #include "BKE_global.h"
+#include "BKE_texture.h"
 
 #include "draw_common.h"
 
@@ -44,6 +46,7 @@
 /* Colors & Constant */
 GlobalsUboStorage ts;
 struct GPUUniformBuffer *globals_ubo = NULL;
+struct GPUTexture *globals_ramp = NULL;
 
 void DRW_globals_update(void)
 {
@@ -110,6 +113,26 @@ void DRW_globals_update(void)
 	}
 
 	globals_ubo = DRW_uniformbuffer_create(sizeof(GlobalsUboStorage), &ts);
+
+	ColorBand ramp = {0};
+	float *colors;
+	int col_size;
+
+	ramp.tot = 3;
+	ramp.data[0].a = 1.0f;
+	ramp.data[0].b = 1.0f;
+	ramp.data[0].pos = 0.0f;
+	ramp.data[1].a = 1.0f;
+	ramp.data[1].g = 1.0f;
+	ramp.data[1].pos = 0.5f;
+	ramp.data[2].a = 1.0f;
+	ramp.data[2].r = 1.0f;
+	ramp.data[2].pos = 1.0f;
+
+	colorband_table_RGBA(&ramp, &colors, &col_size);
+	globals_ramp = GPU_texture_create_1D(col_size, colors, NULL);
+
+	MEM_freeN(colors);
 }
 
 /* ********************************* SHGROUP ************************************* */

source/blender/draw/intern/draw_manager.c

@@ -3265,6 +3265,7 @@ void DRW_engines_register(void)
 }
 
 extern struct GPUUniformBuffer *globals_ubo; /* draw_common.c */
+extern struct GPUTexture *globals_ramp; /* draw_common.c */
 void DRW_engines_free(void)
 {
 	DRW_shape_cache_free();
@@ -3282,6 +3283,9 @@ void DRW_engines_free(void)
 	if (globals_ubo)
 		GPU_uniformbuffer_free(globals_ubo);
 
+	if (globals_ramp)
+		GPU_texture_free(globals_ramp);
+
 #ifdef WITH_CLAY_ENGINE
 	BLI_remlink(&R_engines, &DRW_engine_viewport_clay_type);
 #endif

source/blender/draw/modes/object_mode.c

@@ -43,6 +43,7 @@
 #include "BKE_global.h"
 #include "BKE_particle.h"
 #include "BKE_image.h"
+#include "BKE_texture.h"
 
 #include "ED_view3d.h"
 #include "ED_view3d.h"
@@ -57,6 +58,7 @@
 #include "draw_common.h"
 
 extern struct GPUUniformBuffer *globals_ubo; /* draw_common.c */
+extern struct GPUTexture *globals_ramp; /* draw_common.c */
 extern GlobalsUboStorage ts;
 
 extern char datatoc_object_outline_resolve_frag_glsl[];
@@ -1414,6 +1416,7 @@ static void OBJECT_cache_populate(void *vedata, Object *ob)
 								DRW_shgroup_uniform_vec3(shgrp, "color", ma ? &ma->r : def_prim_col, 1);
 								DRW_shgroup_uniform_vec3(shgrp, "outlineColor", ma ? &ma->specr : def_sec_col, 1);
 								DRW_shgroup_uniform_short_to_int(shgrp, "size", &part->draw_size, 1);
+								DRW_shgroup_uniform_texture(shgrp, "ramp", globals_ramp);
 								DRW_shgroup_call_add(shgrp, geom, mat);
 								break;
 							case PART_DRAW_CROSS:
@@ -1435,9 +1438,11 @@ static void OBJECT_cache_populate(void *vedata, Object *ob)
 						if (draw_as != PART_DRAW_DOT) {
 							DRW_shgroup_attrib_float(shgrp, "pos", 3);
 							DRW_shgroup_attrib_float(shgrp, "rot", 4);
+							DRW_shgroup_attrib_float(shgrp, "val", 1);
 							DRW_shgroup_uniform_vec3(shgrp, "color", &ma->r, 1);
 							DRW_shgroup_uniform_short_to_int(shgrp, "draw_size", &part->draw_size, 1);
 							DRW_shgroup_uniform_float(shgrp, "pixel_size", DRW_viewport_pixelsize_get(), 1);
+							DRW_shgroup_uniform_texture(shgrp, "ramp", globals_ramp);
 							DRW_shgroup_instance_batch(shgrp, geom);
 						}
 					}

source/blender/draw/modes/shaders/object_particle_dot_frag.glsl

@@ -1,8 +1,11 @@
 
 uniform vec3 color;
 uniform vec3 outlineColor;
+uniform sampler1D ramp;
 
 in vec4 radii;
+flat in float finalVal;
+
 out vec4 fragColor;
 
 void main() {
@@ -23,11 +26,23 @@ void main() {
 	float midStroke = 0.5 * (radii[1] + radii[2]);
 
 	if (dist > midStroke) {
-		fragColor.rgb = outlineColor;
+		if (finalVal < 0.0) {
+			fragColor.rgb = outlineColor;
+		}
+		else {
+			fragColor.rgb = texture(ramp, finalVal).rgb;
+		}
+
 		fragColor.a = mix(1.0, 0.0, smoothstep(radii[1], radii[0], dist));
 	}
 	else {
-		fragColor.rgb = mix(color, outlineColor, smoothstep(radii[3], radii[2], dist));
+		if (finalVal < 0.0) {
+			fragColor.rgb = mix(color, outlineColor, smoothstep(radii[3], radii[2], dist));
+		}
+		else {
+			fragColor.rgb = texture(ramp, finalVal).rgb;
+		}
+
 		fragColor.a = 1.0;
 	}
 

source/blender/draw/modes/shaders/object_particle_dot_vert.glsl

@@ -3,7 +3,10 @@ uniform mat4 ModelViewProjectionMatrix;
 uniform int size;
 
 in vec3 pos;
+in float val;
+
 out vec4 radii;
+flat out float finalVal;
 
 void main() {
 	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
@@ -20,4 +23,6 @@ void main() {
 
 	// convert to PointCoord units
 	radii /= size;
+
+	finalVal = val;
 }

source/blender/draw/modes/shaders/object_particle_prim_frag.glsl

@@ -1,14 +1,21 @@
 
 uniform vec3 color;
+uniform sampler1D ramp;
 
 flat in int finalAxis;
+flat in float finalVal;
 
 out vec4 fragColor;
 
 void main()
 {
 	if (finalAxis == -1) {
-		fragColor.rgb = color;
+		if (finalVal < 0.0) {
+			fragColor.rgb = color;
+		}
+		else {
+			fragColor.rgb = texture(ramp, finalVal).rgb;
+		}
 	}
 	else {
 		fragColor.rgb = vec3(0.0);

source/blender/draw/modes/shaders/object_particle_prim_vert.glsl

@@ -9,10 +9,12 @@ uniform int draw_size;
 
 in vec3 pos;
 in vec4 rot;
+in float val;
 in vec3 inst_pos;
 in int axis;
 
 flat out int finalAxis;
+flat out float finalVal;
 
 vec3 rotate(vec3 vec, vec4 quat)
 {
@@ -46,4 +48,5 @@ void main()
 	}
 
 	finalAxis = axis;
+	finalVal = val;
 }