// 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
}
// setTextureMode is used to switch to a repeating
// texture instead of a 1:1 texture mapping.
func (gc *opengl) setTextureMode(tid uint32, repeat bool) {
gl.BindTexture(gl.TEXTURE_2D, tid)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAX_LEVEL, 7)
if repeat {
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT)
} else {
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_MAG_FILTER, gl.LINEAR)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST_MIPMAP_LINEAR)
}
// initRender is one time initialization that creates a single VAO
// to display a single ray trace generated texture.
func (rt *rtrace) initRender() {
rt.verts = []float32{ // four verticies for a quad.
0, 0, 0,
4, 0, 0,
0, 4, 0,
4, 4, 0,
}
rt.faces = []uint8{ // create quad from 2 triangles.
0, 2, 1,
1, 2, 3,
}
rt.uvs = []float32{ // texture coordinates to sample the image.
0, 0,
1, 0,
0, 1,
1, 1,
}
// Start up OpenGL and create a single vertex array object.
gl.Init()
gl.GenVertexArrays(1, &rt.vao)
gl.BindVertexArray(rt.vao)
// vertex data.
var vbuff uint32
gl.GenBuffers(1, &vbuff)
gl.BindBuffer(gl.ARRAY_BUFFER, vbuff)
gl.BufferData(gl.ARRAY_BUFFER, int64(len(rt.verts)*4), gl.Pointer(&(rt.verts[0])), gl.STATIC_DRAW)
gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0)
gl.EnableVertexAttribArray(0)
// faces data.
var ebuff uint32
gl.GenBuffers(1, &ebuff)
gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, ebuff)
gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, int64(len(rt.faces)), gl.Pointer(&(rt.faces[0])), gl.STATIC_DRAW)
// texture coordatinates
var tbuff uint32
gl.GenBuffers(1, &tbuff)
gl.BindBuffer(gl.ARRAY_BUFFER, tbuff)
gl.BufferData(gl.ARRAY_BUFFER, int64(len(rt.uvs)*4), gl.Pointer(&(rt.uvs[0])), gl.STATIC_DRAW)
var tattr uint32 = 2
gl.VertexAttribPointer(tattr, 2, gl.FLOAT, false, 0, 0)
gl.EnableVertexAttribArray(tattr)
// use ray trace generated texture image.
bounds := rt.img.Bounds()
width, height := int32(bounds.Dx()), int32(bounds.Dy())
ptr := gl.Pointer(&(rt.img.Pix[0]))
gl.GenTextures(1, &rt.texId)
gl.BindTexture(gl.TEXTURE_2D, rt.texId)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, ptr)
// texture sampling shader.
loader := load.NewLoader()
shader := "tuv"
vsrc, verr := loader.Vsh(shader)
fsrc, ferr := loader.Fsh(shader)
if verr != nil || ferr != nil {
log.Fatalf("Failed to load shaders %s %s\n", verr, ferr)
}
rt.shaders = gl.CreateProgram()
if err := gl.BindProgram(rt.shaders, vsrc, fsrc); err != nil {
log.Fatalf("Failed to create program: %s\n", err)
}
rt.mvpId = gl.GetUniformLocation(rt.shaders, "mvpm")
rt.tex2D = gl.GetUniformLocation(rt.shaders, "sampler2D")
rt.mvp = render.NewMvp().Set(lin.NewM4().Ortho(0, 4, 0, 4, 0, 10))
// set some state that doesn't need to change during drawing.
gl.ClearColor(0.0, 0.0, 0.0, 1.0)
}