// BindFrame creates a framebuffer object with an associated texture.
// http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-14-render-to-texture/
// http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-16-shadow-mapping/
func (gc *opengl) BindFrame(buf int, fbo, tid, db *uint32) (err error) {
size := int32(1024)
gl.GenFramebuffers(1, fbo)
gl.BindFramebuffer(gl.FRAMEBUFFER, *fbo)
// Create a texture specifically for the framebuffer.
gl.GenTextures(1, tid)
gl.BindTexture(gl.TEXTURE_2D, *tid)
switch buf {
case IMAGE_BUFF:
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, size, size,
0, gl.RGBA, gl.UNSIGNED_BYTE, gl.Pointer(nil))
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)
// Add a depth buffer to mimic the normal framebuffer behaviour for 3D objects.
gl.GenRenderbuffers(1, db)
gl.BindRenderbuffer(gl.RENDERBUFFER, *db)
gl.RenderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT, size, size)
gl.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, *db)
// Associate the texture with the framebuffer.
gl.FramebufferTexture(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, *tid, 0)
buffType := uint32(gl.COLOR_ATTACHMENT0)
gl.DrawBuffers(1, &buffType)
case DEPTH_BUFF:
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.DEPTH_COMPONENT16, size, size,
0, gl.DEPTH_COMPONENT, gl.FLOAT, gl.Pointer(nil))
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_COMPARE_FUNC, gl.LEQUAL)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_COMPARE_MODE, gl.COMPARE_REF_TO_TEXTURE)
// Associate the texture with the framebuffer.
gl.FramebufferTexture(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, *tid, 0)
gl.DrawBuffer(gl.NONE)
default:
return fmt.Errorf("BindFrame unrecognized buffer type.")
}
// Report any problems.
glerr := gl.CheckFramebufferStatus(gl.FRAMEBUFFER)
if glerr != gl.FRAMEBUFFER_COMPLETE {
return fmt.Errorf("BindFrame error %X", glerr)
}
if glerr := gl.GetError(); glerr != gl.NO_ERROR {
err = fmt.Errorf("Failed binding framebuffer %X", glerr)
}
gl.BindFramebuffer(gl.FRAMEBUFFER, 0) // clean up by resetting to default framebuffer.
return err
}
// Render implementation.
// FUTURE: all kinds of possible optimizations that would need to be
// profiled before implementing.
// • group by vao to avoid switching vao's.
// • group by texture to avoid switching textures.
// • use interleaved vertex data.
// • uniform buffers http://www.opengl.org/wiki/Uniform_Buffer_Object.
// • ... lots more possiblities... leave your fav here.
func (gc *opengl) Render(dr Draw) {
d, ok := dr.(*draw)
if !ok || d == nil {
return
}
// switch state only if necessary.
if gc.depthTest != d.depth {
if d.depth {
gl.Enable(gl.DEPTH_TEST)
} else {
gl.Disable(gl.DEPTH_TEST)
}
gc.depthTest = d.depth
}
// switch render framebuffer only if necessary. The framebuffer
// is used to render to a texture associated with a framebuffer.
if gc.fbo != d.fbo {
gl.BindFramebuffer(gl.FRAMEBUFFER, d.fbo)
if d.fbo == 0 {
gl.Viewport(0, 0, gc.vw, gc.vh)
} else {
gl.Clear(gl.DEPTH_BUFFER_BIT)
gl.Viewport(0, 0, 1024, 1024) // size convention for framebuffer texture.
}
gc.fbo = d.fbo
}
// switch shaders only if necessary.
if gc.shader != d.shader {
gl.UseProgram(d.shader)
gc.shader = d.shader
}
// Ask the model to bind its provisioned uniforms.
// FUTURE: only need to bind uniforms that have changed.
gc.bindUniforms(d)
// bind the data buffers and render.
gl.BindVertexArray(d.vao)
switch d.mode {
case LINES:
gl.PolygonMode(gl.FRONT_AND_BACK, gl.LINE)
gl.DrawElements(gl.LINES, d.numFaces, gl.UNSIGNED_SHORT, 0)
gl.PolygonMode(gl.FRONT_AND_BACK, gl.FILL)
case POINTS:
gl.Enable(gl.PROGRAM_POINT_SIZE)
gl.DrawArrays(gl.POINTS, 0, d.numVerts)
gl.Disable(gl.PROGRAM_POINT_SIZE)
case TRIANGLES:
if len(d.texs) > 1 && d.texs[0].fn > 0 {
// Multiple textures on one model specify which verticies they apply to.
for _, tex := range d.texs {
// Use the same texture unit and sampler. Just update which
// image is being sampled.
gl.BindTexture(gl.TEXTURE_2D, tex.tid)
// fn is the number of triangles, 3 indicies per triangle.
// f0 is the offset in triangles where each triangle has 3 indicies
// of 2 bytes (uShort) each.
gl.DrawElements(gl.TRIANGLES, tex.fn*3, gl.UNSIGNED_SHORT, int64(3*2*tex.f0))
}
} else {
// Single textures are handled with a standard bindUniforms
gl.DrawElements(gl.TRIANGLES, d.numFaces, gl.UNSIGNED_SHORT, 0)
}
}
}