1 files changed, 108 insertions, 10 deletions
diff --git a/source/blender/draw/engines/overlay/shaders/volume_velocity_vert.glsl b/source/blender/draw/engines/overlay/shaders/volume_velocity_vert.glsl
index 752694301f7..0b827601f8e 100644
--- a/source/blender/draw/engines/overlay/shaders/volume_velocity_vert.glsl
+++ b/source/blender/draw/engines/overlay/shaders/volume_velocity_vert.glsl
@@ -5,6 +5,8 @@ uniform sampler3D velocityZ;
 uniform float displaySize = 1.0;
 uniform float slicePosition;
 uniform int sliceAxis; /* -1 is no slice, 0 is X, 1 is Y, 2 is Z. */
+uniform bool scaleWithMagnitude = false;
+uniform bool isCellCentered = false;
 
 /* FluidDomainSettings.cell_size */
 uniform vec3 cellSize;
@@ -13,7 +15,15 @@ uniform vec3 domainOriginOffset;
 /* FluidDomainSettings.res_min */
 uniform ivec3 adaptiveCellOffset;
 
+#ifdef USE_MAC
+uniform bool drawMACX;
+uniform bool drawMACY;
+uniform bool drawMACZ;
+
+out vec4 finalColor;
+#else
 flat out vec4 finalColor;
+#endif
 
 const vec3 corners[4] = vec3[4](vec3(0.0, 0.2, -0.5),
                                 vec3(-0.2 * 0.866, -0.2 * 0.5, -0.5),
@@ -64,10 +74,53 @@ mat3 rotation_from_vector(vec3 v)
   return mat3(T, B, N);
 }
 
+vec3 get_vector(ivec3 cell_co)
+{
+  vec3 vector;
+
+  vector.x = texelFetch(velocityX, cell_co, 0).r;
+  vector.y = texelFetch(velocityY, cell_co, 0).r;
+  vector.z = texelFetch(velocityZ, cell_co, 0).r;
+
+  return vector;
+}
+
+/* Interpolate MAC information for cell-centered vectors. */
+vec3 get_vector_centered(ivec3 cell_co)
+{
+  vec3 vector;
+
+  vector.x = 0.5 * (texelFetch(velocityX, cell_co, 0).r +
+                    texelFetch(velocityX, ivec3(cell_co.x + 1, cell_co.yz), 0).r);
+  vector.y = 0.5 * (texelFetch(velocityY, cell_co, 0).r +
+                    texelFetch(velocityY, ivec3(cell_co.x, cell_co.y + 1, cell_co.z), 0).r);
+  vector.z = 0.5 * (texelFetch(velocityZ, cell_co, 0).r +
+                    texelFetch(velocityZ, ivec3(cell_co.xy, cell_co.z + 1), 0).r);
+
+  return vector;
+}
+
+/* Interpolate cell-centered information for MAC vectors. */
+vec3 get_vector_mac(ivec3 cell_co)
+{
+  vec3 vector;
+
+  vector.x = 0.5 * (texelFetch(velocityX, ivec3(cell_co.x - 1, cell_co.yz), 0).r +
+                    texelFetch(velocityX, cell_co, 0).r);
+  vector.y = 0.5 * (texelFetch(velocityY, ivec3(cell_co.x, cell_co.y - 1, cell_co.z), 0).r +
+                    texelFetch(velocityY, cell_co, 0).r);
+  vector.z = 0.5 * (texelFetch(velocityZ, ivec3(cell_co.xy, cell_co.z - 1), 0).r +
+                    texelFetch(velocityZ, cell_co, 0).r);
+
+  return vector;
+}
+
 void main()
 {
 #ifdef USE_NEEDLE
   int cell = gl_VertexID / 12;
+#elif defined(USE_MAC)
+  int cell = gl_VertexID / 6;
 #else
   int cell = gl_VertexID / 2;
 #endif
@@ -97,19 +150,64 @@ void main()
 
   vec3 pos = domainOriginOffset + cellSize * (vec3(cell_co + adaptiveCellOffset) + 0.5);
 
-  vec3 velocity;
-  velocity.x = texelFetch(velocityX, cell_co, 0).r;
-  velocity.y = texelFetch(velocityY, cell_co, 0).r;
-  velocity.z = texelFetch(velocityZ, cell_co, 0).r;
+  vec3 vector;
+
+#ifdef USE_MAC
+  vec3 color;
+  vector = (isCellCentered) ? get_vector_mac(cell_co) : get_vector(cell_co);
+
+  switch (gl_VertexID % 6) {
+    case 0: /* Tail of X component. */
+      pos.x += (drawMACX) ? -0.5 * cellSize.x : 0.0;
+      color = vec3(1.0, 0.0, 0.0); /* red */
+      break;
+    case 1: /* Head of X component. */
+      pos.x += (drawMACX) ? (-0.5 + vector.x * displaySize) * cellSize.x : 0.0;
+      color = vec3(1.0, 1.0, 0.0); /* yellow */
+      break;
+    case 2: /* Tail of Y component. */
+      pos.y += (drawMACY) ? -0.5 * cellSize.y : 0.0;
+      color = vec3(0.0, 1.0, 0.0); /* green */
+      break;
+    case 3: /* Head of Y component. */
+      pos.y += (drawMACY) ? (-0.5 + vector.y * displaySize) * cellSize.y : 0.0;
+      color = vec3(1.0, 1.0, 0.0); /* yellow */
+      break;
+    case 4: /* Tail of Z component. */
+      pos.z += (drawMACZ) ? -0.5 * cellSize.z : 0.0;
+      color = vec3(0.0, 0.0, 1.0); /* blue */
+      break;
+    case 5: /* Head of Z component. */
+      pos.z += (drawMACZ) ? (-0.5 + vector.z * displaySize) * cellSize.z : 0.0;
+      color = vec3(1.0, 1.0, 0.0); /* yellow */
+      break;
+  }
 
-  finalColor = vec4(weight_to_color(length(velocity)), 1.0);
+  finalColor = vec4(color, 1.0);
+#else
+  vector = (isCellCentered) ? get_vector(cell_co) : get_vector_centered(cell_co);
 
-#ifdef USE_NEEDLE
-  mat3 rot_mat = rotation_from_vector(velocity);
+  finalColor = vec4(weight_to_color(length(vector)), 1.0);
+
+  float vector_length = 1.0;
+
+  if (scaleWithMagnitude) {
+    vector_length = length(vector);
+  }
+  else if (length(vector) == 0.0) {
+    vector_length = 0.0;
+  }
+
+  mat3 rot_mat = rotation_from_vector(vector);
+
+#  ifdef USE_NEEDLE
   vec3 rotated_pos = rot_mat * corners[indices[gl_VertexID % 12]];
-  pos += rotated_pos * length(velocity) * displaySize * cellSize;
-#else
-  pos += ((gl_VertexID % 2) == 1) ? velocity * displaySize * cellSize : vec3(0.0);
+  pos += rotated_pos * vector_length * displaySize * cellSize;
+#  else
+  vec3 rotated_pos = rot_mat * vec3(0.0, 0.0, 1.0);
+  pos += ((gl_VertexID % 2) == 1) ? rotated_pos * vector_length * displaySize * cellSize :
+                                    vec3(0.0);
+#  endif
 #endif
 
   vec3 world_pos = point_object_to_world(pos);