Gawain: batch rendering API

Follow-up to rBddb1d5648dbd

API is nearly complete but untested.

1) create batch with vertex buffer & optional index buffer
2) choose shader program
3) draw!

1 files changed, 42 insertions, 88 deletions

diff --git a/source/blender/gpu/gawain/batch.h b/source/blender/gpu/gawain/batch.h
index 9625d666a41..8387b0144a3 100644
--- a/source/blender/gpu/gawain/batch.h
+++ b/source/blender/gpu/gawain/batch.h
@@ -13,34 +13,53 @@
 
 #include "vertex_buffer.h"
 #include "element.h"
-#include "attrib_binding.h"
-
-// How will this API be used?
-// create batch
-// ...
-// profit!
-
-// TODO: finalize Batch struct design & usage, pare down this file
-
-typedef struct {
-	VertexBuffer; // format is fixed at "vec3 pos"
-	ElementList line_elem;
-	ElementList triangle_elem;
-	GLuint vao_id;
-	GLenum prev_prim; // did most recent draw use GL_POINTS, GL_LINES or GL_TRIANGLES?
-} BasicBatch;
-
-// How to do this without replicating code?
 
 typedef struct {
+	// geometry
 	VertexBuffer* verts;
-	ElementList* elem; // <-- NULL if element list not needed
+	ElementList* elem; // NULL if element list not needed
 	GLenum prim_type;
-	GLuint vao_id;
-	GLuint bound_program;
-	AttribBinding attrib_binding;
+
+	// book-keeping
+	GLuint vao_id; // remembers all geometry state (vertex attrib bindings & element buffer)
+	bool program_dirty;
+
+	// state
+	GLuint program;
 } Batch;
 
+Batch* Batch_create(GLenum prim_type, VertexBuffer*, ElementList*);
+
+void Batch_set_program(Batch*, GLuint program);
+// Entire batch draws with one shader program, but can be redrawn later with another program.
+// Vertex shader's inputs must be compatible with the batch's vertex format.
+
+void Batch_draw(Batch*);
+
+
+
+
+
+
+#if 0 // future plans
+
+// Can multiple batches share a VertexBuffer? Use ref count?
+
+
+// for multithreaded batch building:
+typedef enum {
+	READY_TO_FORMAT,
+	READY_TO_BUILD,
+	BUILDING, BUILDING_IMM, // choose one
+	READY_TO_DRAW
+} BatchPhase;
+
+
+Batch* immBeginBatch(GLenum prim_type, unsigned v_ct);
+// use standard immFunctions after this. immEnd will finalize the batch instead
+// of drawing.
+
+
 // We often need a batch with its own data, to be created and discarded together.
 // WithOwn variants reduce number of system allocations.
 
@@ -67,69 +86,4 @@ Batch* create_BatchWithOwnVertexBufferAndElementList(GLenum prim_type, VertexFor
 // elem: none, shared, own
 Batch* create_BatchInGeneral(GLenum prim_type, VertexBufferStuff, ElementListStuff);
 
-typedef struct {
-	// geometry
-	GLenum prim_type;
-	VertexBuffer verts;
-	ElementList elem; // <-- elem.index_ct = 0 if element list not needed
-
-	// book-keeping
-	GLuint vao_id; // <-- remembers all vertex state (array buffer, element buffer, attrib bindings)
-	// wait a sec... I thought VAO held attrib bindings but not currently bound array buffer.
-	// That's fine but verify that VAO holds *element* buffer binding.
-	// Verified: ELEMENT_ARRAY_BUFFER_BINDING is part of VAO state.
-	// VERTEX_ATTRIB_ARRAY_BUFFER_BINDING is too, per vertex attrib. Currently bound ARRAY_BUFFER is not.
-	// Does APPLE_vertex_array_object also include ELEMENT_ARRAY_BUFFER_BINDING?
-	// The extension spec refers only to APPLE_element_array, so.. maybe, maybe not?
-	// Will have to test during development, maybe alter behavior for APPLE_LEGACY. Can strip out this
-	// platform-specific cruft for Blender, keep it for legacy Gawain.
-
-	// state
-	GLuint bound_program;
-	AttribBinding attrib_binding;
-} Batch;
-
-typedef struct {
-	Batch* batch;
-} BatchBuilder;
-
-// One batch can be drawn with multiple shaders, as long as those shaders' inputs
-// are compatible with the batch's vertex format.
-
-// Can multiple batches share a VertexBuffer? Use ref count?
-
-// BasicBatch
-// Create one VertexBuffer from an object's verts (3D position only)
-// Shader must depend only on position + uniforms: uniform color, depth only, or object ID.
-// - draw verts via DrawArrays
-// - draw lines via DrawElements (can have 2 element lists: true face edges, triangulated edges)
-// - draw faces via DrawElements (raw triangles, not polygon faces)
-// This is very 3D-mesh-modeling specific. I'm investigating what Gawain needs to allow/expose
-// to meet Blender's needs, possibly other programs' needs.
-
-Batch* BatchPlease(GLenum prim_type, unsigned prim_ct, unsigned v_ct);
-//                   GL_TRIANGLES   12 triangles that share 8 vertices
-
-// Is there ever a reason to index GL_POINTS? nothing comes to mind...
-// (later) ok now that I'm thinking straight, *of course* you can draw
-// indexed POINTS. Only some verts from the buffer will be drawn. I was
-// just limiting my thinking to immediate needs. Batched needs.
-
-Batch* batch = BatchPlease(GL_TRIANGLES, 12, 8);
-unsigned pos = add_attrib(batch->verts.format, "pos", GL_FLOAT, 3, KEEP_FLOAT);
-pack(batch->verts->format); // or ...
-finalize(batch); // <-- packs vertex format, allocates vertex buffer
-
-Batch* create_Batch(GLenum prim_type, VertexBuffer*, ElementList*);
-
-// and don't forget
-Batch* immBeginBatch(GLenum prim_type, unsigned v_ct);
-// use standard immFunctions after this. immEnd will finalize the batch instead
-// of drawing.
-
-typedef enum {
-	READY_TO_FORMAT,
-	READY_TO_BUILD,
-	BUILDING, BUILDING_IMM, // choose one
-	READY_TO_DRAW
-} BatchPhase;
+#endif // future plans