OpenGL: immediate mode work-alike

Introducing an immediate mode drawing API that works with modern GL 3.2
core profile. I wrote and tested this using a core context on Mac.

This is part of the Gawain library which is Apache 2 licensed. Be very
careful not to pull other Blender code into these files.

Modifications for the Blender integration:
- prefix filenames to match rest of Blender’s GPU libs
- include GPU_glew.h instead of <OpenGL/gl3.h>
- disable thread-local vars until we figure out how best to do this

1 files changed, 67 insertions, 0 deletions

diff --git a/source/blender/gpu/GPU_immediate.h b/source/blender/gpu/GPU_immediate.h
new file mode 100644
index 00000000000..aeed133645c
--- /dev/null
+++ b/source/blender/gpu/GPU_immediate.h
@@ -0,0 +1,67 @@
+
+// Gawain immediate mode work-alike, take 2
+//
+// This code is part of the Gawain library, with modifications
+// specific to integration with Blender.
+//
+// Copyright 2016 Mike Erwin
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+
+#pragma once
+
+#include "GPU_glew.h"
+#include <stdbool.h>
+
+#define PER_THREAD
+// #define PER_THREAD __thread
+// MSVC uses __declspec(thread) for C code
+
+#define MAX_VERTEX_ATTRIBS 16
+
+#define TRUST_NO_ONE 1
+
+typedef enum {
+	KEEP_FLOAT,
+	KEEP_INT,
+	NORMALIZE_INT_TO_FLOAT, // 127 (ubyte) -> 0.5 (and so on for other int types)
+	CONVERT_INT_TO_FLOAT // 127 (any int type) -> 127.0
+} VertexFetchMode;
+
+typedef struct {
+	GLenum comp_type;
+	unsigned comp_ct; // 1 to 4
+	unsigned sz; // size in bytes, 1 to 16
+	unsigned offset; // from beginning of vertex, in bytes
+	VertexFetchMode fetch_mode;
+	char* name; // TODO: shared allocation of all names within a VertexFormat
+} Attrib;
+
+typedef struct {
+	unsigned attrib_ct; // 0 to 16 (MAX_VERTEX_ATTRIBS)
+	unsigned stride; // stride in bytes, 1 to 256
+	bool packed;
+	Attrib attribs[MAX_VERTEX_ATTRIBS]; // TODO: variable-size attribs array
+} VertexFormat;
+
+void clear_VertexFormat(VertexFormat*);
+unsigned add_attrib(VertexFormat*, const char* name, GLenum comp_type, unsigned comp_ct, VertexFetchMode);
+void pack(VertexFormat*);
+// unsigned attrib_idx(const VertexFormat*, const char* name);
+void bind_attrib_locations(const VertexFormat*, GLuint program);
+
+extern PER_THREAD VertexFormat immVertexFormat; // so we don't have to copy or pass around
+
+void immInit(void);
+void immDestroy(void);
+
+void immBegin(GLenum primitive, unsigned vertex_ct);
+void immEnd(void);
+
+void immAttrib1f(unsigned attrib_id, float x);
+void immAttrib3f(unsigned attrib_id, float x, float y, float z);
+
+void immEndVertex(void); // and move on to the next vertex