Properly fix blend equations for both transparent and non transparent framebuffers. Closes #15047

drivers/gles3/rasterizer_canvas_gles3.cpp

@@ -1175,28 +1175,46 @@ void RasterizerCanvasGLES3::canvas_render_items(Item *p_item_list, int p_z, cons
 					if (storage->frame.current_rt && storage->frame.current_rt->flags[RasterizerStorage::RENDER_TARGET_TRANSPARENT]) {
 						glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
 					} else {
-						glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+						glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ZERO, GL_ONE);
 					}
 
 				} break;
 				case RasterizerStorageGLES3::Shader::CanvasItem::BLEND_MODE_ADD: {
 
 					glBlendEquation(GL_FUNC_ADD);
-					glBlendFunc(GL_SRC_ALPHA, GL_ONE);
+					if (storage->frame.current_rt && storage->frame.current_rt->flags[RasterizerStorage::RENDER_TARGET_TRANSPARENT]) {
+						glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_SRC_ALPHA, GL_ONE);
+					} else {
+						glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_ZERO, GL_ONE);
+					}
 
 				} break;
 				case RasterizerStorageGLES3::Shader::CanvasItem::BLEND_MODE_SUB: {
 
 					glBlendEquation(GL_FUNC_REVERSE_SUBTRACT);
-					glBlendFunc(GL_SRC_ALPHA, GL_ONE);
+					if (storage->frame.current_rt && storage->frame.current_rt->flags[RasterizerStorage::RENDER_TARGET_TRANSPARENT]) {
+						glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_SRC_ALPHA, GL_ONE);
+					} else {
+						glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_ZERO, GL_ONE);
+					}
 				} break;
 				case RasterizerStorageGLES3::Shader::CanvasItem::BLEND_MODE_MUL: {
 					glBlendEquation(GL_FUNC_ADD);
-					glBlendFunc(GL_DST_COLOR, GL_ZERO);
+					if (storage->frame.current_rt && storage->frame.current_rt->flags[RasterizerStorage::RENDER_TARGET_TRANSPARENT]) {
+						glBlendFuncSeparate(GL_DST_COLOR, GL_ZERO, GL_DST_ALPHA, GL_ZERO);
+					} else {
+						glBlendFuncSeparate(GL_DST_COLOR, GL_ZERO, GL_ZERO, GL_ONE);
+					}
+
 				} break;
 				case RasterizerStorageGLES3::Shader::CanvasItem::BLEND_MODE_PMALPHA: {
 					glBlendEquation(GL_FUNC_ADD);
-					glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+					if (storage->frame.current_rt && storage->frame.current_rt->flags[RasterizerStorage::RENDER_TARGET_TRANSPARENT]) {
+						glBlendFuncSeparate(GL_ONE, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+					} else {
+						glBlendFuncSeparate(GL_ONE, GL_ONE_MINUS_SRC_ALPHA, GL_ZERO, GL_ONE);
+					}
+
 				} break;
 			}