Render: add "OpenGL" render engine.

This is intended for quick renders for previsualization, animation previews
or sequencer previews. It provides the same settings as found in the 3D view
Shading popover in solid display mode, but in the scene render properties.

The "Workbench" engine was removed, and this name no longer appears in the
user interface, it's purely an internal name. We might come up with a better
name for this OpenGL engine still, but it's good to be consistent with the
OpenGL Render operator name since this has a similar purpose.

4 files changed, 56 insertions, 1 deletions

diff --git a/source/blender/draw/intern/DRW_render.h b/source/blender/draw/intern/DRW_render.h
index a4a933250c9..16a17f4f21d 100644
--- a/source/blender/draw/intern/DRW_render.h
+++ b/source/blender/draw/intern/DRW_render.h
@@ -226,6 +226,7 @@ void DRW_uniformbuffer_free(struct GPUUniformBuffer *ubo);
 } while (0)
 
 void DRW_transform_to_display(struct GPUTexture *tex);
+void DRW_transform_none(struct GPUTexture *tex);
 void DRW_multisamples_resolve(
         struct GPUTexture *src_depth, struct GPUTexture *src_color);
 
diff --git a/source/blender/draw/intern/draw_cache.c b/source/blender/draw/intern/draw_cache.c
index 707aadbc229..d23b9e693ce 100644
--- a/source/blender/draw/intern/draw_cache.c
+++ b/source/blender/draw/intern/draw_cache.c
@@ -51,6 +51,7 @@ static struct DRWShapeCache {
 	Gwn_Batch *drw_cursor;
 	Gwn_Batch *drw_cursor_only_circle;
 	Gwn_Batch *drw_fullscreen_quad;
+	Gwn_Batch *drw_fullscreen_quad_texcoord;
 	Gwn_Batch *drw_quad;
 	Gwn_Batch *drw_sphere;
 	Gwn_Batch *drw_screenspace_circle;
@@ -287,6 +288,35 @@ Gwn_Batch *DRW_cache_fullscreen_quad_get(void)
 	return SHC.drw_fullscreen_quad;
 }
 
+Gwn_Batch *DRW_cache_fullscreen_quad_texcoord_get(void)
+{
+	if (!SHC.drw_fullscreen_quad_texcoord) {
+		/* Use a triangle instead of a real quad */
+		/* https://www.slideshare.net/DevCentralAMD/vertex-shader-tricks-bill-bilodeau - slide 14 */
+		float pos[3][2] = {{-1.0f, -1.0f}, { 3.0f, -1.0f}, {-1.0f,  3.0f}};
+		float texCoord[3][2] = {{ 0.0f,  0.0f}, { 2.0f,  0.0f}, { 0.0f,  2.0f}};
+
+		/* Position Only 2D format */
+		static Gwn_VertFormat format = { 0 };
+		static struct { uint pos, texCoord; } attr_id;
+		if (format.attr_len == 0) {
+			attr_id.pos = GWN_vertformat_attr_add(&format, "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+			attr_id.texCoord = GWN_vertformat_attr_add(&format, "texCoord", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+		}
+
+		Gwn_VertBuf *vbo = GWN_vertbuf_create_with_format(&format);
+		GWN_vertbuf_data_alloc(vbo, 3);
+
+		for (int i = 0; i < 3; ++i) {
+			GWN_vertbuf_attr_set(vbo, attr_id.pos, i, pos[i]);
+			GWN_vertbuf_attr_set(vbo, attr_id.texCoord, i, texCoord[i]);
+		}
+
+		SHC.drw_fullscreen_quad_texcoord = GWN_batch_create_ex(GWN_PRIM_TRIS, vbo, NULL, GWN_BATCH_OWNS_VBO);
+	}
+	return SHC.drw_fullscreen_quad_texcoord;
+}
+
 /* Just a regular quad with 4 vertices. */
 Gwn_Batch *DRW_cache_quad_get(void)
 {
diff --git a/source/blender/draw/intern/draw_cache.h b/source/blender/draw/intern/draw_cache.h
index c1c80d2c5bf..07c8a571256 100644
--- a/source/blender/draw/intern/draw_cache.h
+++ b/source/blender/draw/intern/draw_cache.h
@@ -40,6 +40,7 @@ struct Gwn_Batch *DRW_cache_cursor_get(bool crosshair_lines);
 
 /* Common Shapes */
 struct Gwn_Batch *DRW_cache_fullscreen_quad_get(void);
+struct Gwn_Batch *DRW_cache_fullscreen_quad_texcoord_get(void);
 struct Gwn_Batch *DRW_cache_quad_get(void);
 struct Gwn_Batch *DRW_cache_cube_get(void);
 struct Gwn_Batch *DRW_cache_sphere_get(void);
diff --git a/source/blender/draw/intern/draw_manager.c b/source/blender/draw/intern/draw_manager.c
index 556f02c2899..58ce9dd5218 100644
--- a/source/blender/draw/intern/draw_manager.c
+++ b/source/blender/draw/intern/draw_manager.c
@@ -283,6 +283,29 @@ void DRW_transform_to_display(GPUTexture *tex)
 	}
 }
 
+/* Draw texture to framebuffer without any color transforms */
+void DRW_transform_none(GPUTexture *tex)
+{
+	/* Draw as texture for final render (without immediate mode). */
+	Gwn_Batch *geom = DRW_cache_fullscreen_quad_texcoord_get();
+	GWN_batch_program_set_builtin(geom, GPU_SHADER_2D_IMAGE_COLOR);
+
+	GPU_texture_bind(tex, 0);
+
+	const float white[4] = {1.0f, 1.0f, 1.0f, 1.0f};
+	GWN_batch_uniform_4fv(geom, "color", white);
+
+	float mat[4][4];
+	unit_m4(mat);
+	GWN_batch_uniform_mat4(geom, "ModelViewProjectionMatrix", mat);
+
+	GWN_batch_program_use_begin(geom);
+	GWN_batch_draw_range_ex(geom, 0, 0, false);
+	GWN_batch_program_use_end(geom);
+
+	GPU_texture_unbind(tex);
+}
+
 /** \} */
 
 
@@ -2217,8 +2240,8 @@ void DRW_engine_register(DrawEngineType *draw_engine_type)
 
 void DRW_engines_register(void)
 {
+	RE_engines_register(&DRW_engine_viewport_opengl_type);
 	RE_engines_register(&DRW_engine_viewport_eevee_type);
-	RE_engines_register(&DRW_engine_viewport_workbench_type);
 
 	DRW_engine_register(&draw_engine_workbench_solid);
 	DRW_engine_register(&draw_engine_workbench_transparent);