1 files changed, 74 insertions, 0 deletions
diff --git a/source/blender/gpu/GPU_primitive.h b/source/blender/gpu/GPU_primitive.h
index 4860b037bfb..de2feac2607 100644
--- a/source/blender/gpu/GPU_primitive.h
+++ b/source/blender/gpu/GPU_primitive.h
@@ -9,6 +9,7 @@
 
 #pragma once
 
+#include "BLI_assert.h"
 #include "GPU_common.h"
 
 #ifdef __cplusplus
@@ -42,6 +43,79 @@ typedef enum {
   GPU_PRIM_CLASS_ANY = GPU_PRIM_CLASS_POINT | GPU_PRIM_CLASS_LINE | GPU_PRIM_CLASS_SURFACE,
 } GPUPrimClass;
 
+inline int gpu_get_prim_count_from_type(uint vertex_len, GPUPrimType prim_type)
+{
+  /* does vertex_len make sense for this primitive type? */
+  if (vertex_len == 0) {
+    return 0;
+  }
+
+  switch (prim_type) {
+    case GPU_PRIM_POINTS:
+      return vertex_len;
+
+    case GPU_PRIM_LINES:
+      BLI_assert(vertex_len % 2 == 0);
+      return vertex_len / 2;
+
+    case GPU_PRIM_LINE_STRIP:
+      return vertex_len - 1;
+
+    case GPU_PRIM_LINE_LOOP:
+      return vertex_len;
+
+    case GPU_PRIM_LINES_ADJ:
+      BLI_assert(vertex_len % 4 == 0);
+      return vertex_len / 4;
+
+    case GPU_PRIM_LINE_STRIP_ADJ:
+      return vertex_len - 2;
+
+    case GPU_PRIM_TRIS:
+      BLI_assert(vertex_len % 3 == 0);
+      return vertex_len / 3;
+
+    case GPU_PRIM_TRI_STRIP:
+      BLI_assert(vertex_len >= 3);
+      return vertex_len - 2;
+
+    case GPU_PRIM_TRI_FAN:
+      BLI_assert(vertex_len >= 3);
+      return vertex_len - 2;
+
+    case GPU_PRIM_TRIS_ADJ:
+      BLI_assert(vertex_len % 6 == 0);
+      return vertex_len / 6;
+
+    default:
+      BLI_assert_unreachable();
+      return 0;
+  }
+}
+
+inline bool is_restart_compatible(GPUPrimType type)
+{
+  switch (type) {
+    case GPU_PRIM_POINTS:
+    case GPU_PRIM_LINES:
+    case GPU_PRIM_TRIS:
+    case GPU_PRIM_LINES_ADJ:
+    case GPU_PRIM_TRIS_ADJ:
+    case GPU_PRIM_NONE:
+    default: {
+      return false;
+    }
+    case GPU_PRIM_LINE_STRIP:
+    case GPU_PRIM_LINE_LOOP:
+    case GPU_PRIM_TRI_STRIP:
+    case GPU_PRIM_TRI_FAN:
+    case GPU_PRIM_LINE_STRIP_ADJ: {
+      return true;
+    }
+  }
+  return false;
+}
+
 /**
  * TODO: Improve error checking by validating that the shader is suited for this primitive type.
  * GPUPrimClass GPU_primtype_class(GPUPrimType);