Cleanup: refactoring of bake code in preparation of vertex color baking

Split of internal/external image bake target code off into smaller functions and
refactor associated data structures for clarity. Designed so that a vertex color
bake target is easy to fit in.

Also avoid passing in a huge number of arguments into the main baking function,
pass a struct instead.

source/blender/render/RE_bake.h

@@ -39,11 +39,23 @@ typedef struct BakeImage {
   size_t offset;
 } BakeImage;
 
-typedef struct BakeImages {
-  BakeImage *data; /* all the images of an object */
-  int *lookup;     /* lookup table from Material to BakeImage */
-  int size;
-} BakeImages;
+typedef struct BakeTargets {
+  /* All images of the object. */
+  BakeImage *images;
+  int num_images;
+
+  /* Lookup table from Material number to BakeImage. */
+  int *material_to_image;
+  int num_materials;
+
+  /* Pixel buffer to bake to. */
+  float *result;
+  int num_pixels;
+  int num_channels;
+
+  /* Baking to non-color data image. */
+  bool is_noncolor;
+} BakeTargets;
 
 typedef struct BakePixel {
   int primitive_id, object_id;
@@ -70,8 +82,7 @@ bool RE_bake_engine(struct Render *re,
                     struct Object *object,
                     const int object_id,
                     const BakePixel pixel_array[],
-                    const BakeImages *bake_images,
-                    const int depth,
+                    const BakeTargets *targets,
                     const eScenePassType pass_type,
                     const int pass_filter,
                     float result[]);
@@ -95,7 +106,7 @@ bool RE_bake_pixels_populate_from_objects(struct Mesh *me_low,
 void RE_bake_pixels_populate(struct Mesh *me,
                              struct BakePixel *pixel_array,
                              const size_t num_pixels,
-                             const struct BakeImages *bake_images,
+                             const struct BakeTargets *targets,
                              const char *uv_layer);
 
 void RE_bake_mask_fill(const BakePixel pixel_array[], const size_t num_pixels, char *mask);

source/blender/render/intern/bake.c

@@ -691,7 +691,7 @@ static void bake_differentials(BakeDataZSpan *bd,
 void RE_bake_pixels_populate(Mesh *me,
                              BakePixel pixel_array[],
                              const size_t num_pixels,
-                             const BakeImages *bake_images,
+                             const BakeTargets *targets,
                              const char *uv_layer)
 {
   const MLoopUV *mloopuv;
@@ -709,7 +709,7 @@ void RE_bake_pixels_populate(Mesh *me,
 
   BakeDataZSpan bd;
   bd.pixel_array = pixel_array;
-  bd.zspan = MEM_callocN(sizeof(ZSpan) * bake_images->size, "bake zspan");
+  bd.zspan = MEM_callocN(sizeof(ZSpan) * targets->num_images, "bake zspan");
 
   /* initialize all pixel arrays so we know which ones are 'blank' */
   for (int i = 0; i < num_pixels; i++) {
@@ -717,8 +717,8 @@ void RE_bake_pixels_populate(Mesh *me,
     pixel_array[i].object_id = 0;
   }
 
-  for (int i = 0; i < bake_images->size; i++) {
-    zbuf_alloc_span(&bd.zspan[i], bake_images->data[i].width, bake_images->data[i].height);
+  for (int i = 0; i < targets->num_images; i++) {
+    zbuf_alloc_span(&bd.zspan[i], targets->images[i].width, targets->images[i].height);
   }
 
   const int tottri = poly_to_tri_count(me->totpoly, me->totloop);
@@ -731,13 +731,13 @@ void RE_bake_pixels_populate(Mesh *me,
     const MPoly *mp = &me->mpoly[lt->poly];
     float vec[3][2];
     int mat_nr = mp->mat_nr;
-    int image_id = bake_images->lookup[mat_nr];
+    int image_id = targets->material_to_image[mat_nr];
 
     if (image_id < 0) {
       continue;
     }
 
-    bd.bk_image = &bake_images->data[image_id];
+    bd.bk_image = &targets->images[image_id];
     bd.primitive_id = i;
 
     for (int a = 0; a < 3; a++) {
@@ -755,7 +755,7 @@ void RE_bake_pixels_populate(Mesh *me,
     zspan_scanconvert(&bd.zspan[image_id], (void *)&bd, vec[0], vec[1], vec[2], store_bake_pixel);
   }
 
-  for (int i = 0; i < bake_images->size; i++) {
+  for (int i = 0; i < targets->num_images; i++) {
     zbuf_free_span(&bd.zspan[i]);
   }
 

source/blender/render/intern/engine.c

@@ -663,8 +663,7 @@ bool RE_bake_engine(Render *re,
                     Object *object,
                     const int object_id,
                     const BakePixel pixel_array[],
-                    const BakeImages *bake_images,
-                    const int depth,
+                    const BakeTargets *targets,
                     const eScenePassType pass_type,
                     const int pass_filter,
                     float result[])
@@ -707,14 +706,14 @@ bool RE_bake_engine(Render *re,
       type->update(engine, re->main, engine->depsgraph);
     }
 
-    for (int i = 0; i < bake_images->size; i++) {
-      const BakeImage *image = bake_images->data + i;
+    for (int i = 0; i < targets->num_images; i++) {
+      const BakeImage *image = targets->images + i;
 
       engine->bake.pixels = pixel_array + image->offset;
-      engine->bake.result = result + image->offset * depth;
+      engine->bake.result = result + image->offset * targets->num_channels;
       engine->bake.width = image->width;
       engine->bake.height = image->height;
-      engine->bake.depth = depth;
+      engine->bake.depth = targets->num_channels;
       engine->bake.object_id = object_id;
 
       type->bake(