add initGLBackingBuffer helper function

include/shader.h

@@ -196,6 +196,13 @@ GLBuffer* getUBOByName(GLContext* gl_ctx, const char* name);
 
 GLTexture* getGLTexture(GLContext* gl_ctx, Texture* diffuse_img);
 
+GLBuffer* initGLBackingBuffer(GLContext* gl_ctx,
+	MemoryArena* arena,
+	const char* name,
+	GLenum data_type,
+	u32 buf_size,
+	void* data);
+
 void updateGLBuffer(GLBuffer* gl_buf, void* data);
 
 void renderVAO(GLMesh* glmesh,

src/shader.cpp

@@ -220,6 +220,28 @@ getGLTexture(GLContext* gl_ctx, Texture* diffuse_img)
 	return nullptr;
 }
 
+GLBuffer* initGLBackingBuffer(GLContext* gl_ctx,
+	MemoryArena* arena,
+	const char* name,
+	GLenum data_type,
+	u32 buf_size,
+	void* data)
+{
+	GLBuffer* buf = getFreeUBO(gl_ctx);
+	glGenBuffers(1, &buf->id);
+	buf->target = GL_UNIFORM_BUFFER;
+	buf->data_type = data_type;
+	buf->data_size = buf_size;
+	buf->name = arenaCopyCStr(arena, name);
+
+	glBindBuffer(buf->target, buf->id);
+	glBufferData(buf->target, buf->data_size, data, GL_DYNAMIC_DRAW);
+	buf->binding_idx = gl_ctx->binding_count++;
+	glBindBufferBase(buf->target, buf->binding_idx, buf->id);
+
+	return buf;
+}
+
 void
 updateGLBuffer(GLBuffer* gl_buf, void* data)
 {