// 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 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)
}
}
}
// initScene is called once on startup to load the 3D data.
func (ld *ldtag) initScene() {
ld.persp = lin.NewM4()
ld.mvp64 = lin.NewM4()
ld.mvp = render.NewMvp()
gl.Init()
ldr := load.NewLoader()
meshes, _ := ldr.Obj("monkey")
mesh := meshes[0]
ld.faceCount = int32(len(mesh.F))
// Gather the one scene into this one vertex array object.
gl.GenVertexArrays(1, &ld.vao)
gl.BindVertexArray(ld.vao)
// vertex data.
var vbuff uint32
gl.GenBuffers(1, &vbuff)
gl.BindBuffer(gl.ARRAY_BUFFER, vbuff)
gl.BufferData(gl.ARRAY_BUFFER, int64(len(mesh.V)*4), gl.Pointer(&(mesh.V[0])), gl.STATIC_DRAW)
gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0)
gl.EnableVertexAttribArray(0)
// normal data.
var nbuff uint32
gl.GenBuffers(1, &nbuff)
gl.BindBuffer(gl.ARRAY_BUFFER, nbuff)
gl.BufferData(gl.ARRAY_BUFFER, int64(len(mesh.N)*4), gl.Pointer(&(mesh.N[0])), gl.STATIC_DRAW)
gl.VertexAttribPointer(1, 3, gl.FLOAT, false, 0, 0)
gl.EnableVertexAttribArray(1)
// faces data, uint32 in this case, so 4 bytes per element.
var fbuff uint32
gl.GenBuffers(1, &fbuff)
gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, fbuff)
gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, int64(len(mesh.F)*2), gl.Pointer(&(mesh.F[0])), gl.STATIC_DRAW)
ld.initShader()
gl.ClearColor(0.2, 0.2, 0.2, 1.0)
gl.Enable(gl.DEPTH_TEST)
gl.Enable(gl.CULL_FACE)
// set the initial perspetive matrix.
ld.resize(0, 0, 800, 600)
}
// Renderer implementation.
func (gc *opengl) Enable(attribute uint32, enabled bool) {
switch attribute {
case CULL, DEPTH:
if enabled {
gl.Enable(attribute)
} else {
gl.Disable(attribute)
}
case BLEND:
if enabled {
gl.Enable(attribute)
// Using non pre-multiplied alpha colour data so...
gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
} else {
gl.Disable(attribute)
}
}
}
// initScene is one time initialization that creates a single VAO
func (tag *trtag) initScene() {
tag.mvp64 = lin.NewM4()
tag.persp = lin.NewM4().Persp(60, float64(600)/float64(600), 0.1, 50)
tag.mvp = render.NewMvp()
tag.initData()
// Bind the OpenGL calls and dump some version info.
gl.Init()
fmt.Printf("%s %s", gl.GetString(gl.RENDERER), gl.GetString(gl.VERSION))
fmt.Printf(" GLSL %s\n", gl.GetString(gl.SHADING_LANGUAGE_VERSION))
// Gather the one scene into this one vertex array object.
gl.GenVertexArrays(1, &tag.vao)
gl.BindVertexArray(tag.vao)
// create shaders
tag.initShader()
gl.UseProgram(tag.shaders)
// vertex data.
var vbuff uint32
gl.GenBuffers(1, &vbuff)
gl.BindBuffer(gl.ARRAY_BUFFER, vbuff)
gl.BufferData(gl.ARRAY_BUFFER, int64(len(tag.verticies)*4), gl.Pointer(&(tag.verticies[0])), gl.STATIC_DRAW)
vattr := uint32(gl.GetAttribLocation(tag.shaders, "in_v"))
gl.EnableVertexAttribArray(vattr)
gl.VertexAttribPointer(vattr, 3, gl.FLOAT, false, 0, 0)
// colour data.
var cbuff uint32
gl.GenBuffers(1, &cbuff)
gl.BindBuffer(gl.ARRAY_BUFFER, cbuff)
gl.BufferData(gl.ARRAY_BUFFER, int64(len(tag.colour)*4), gl.Pointer(&(tag.colour[0])), gl.STATIC_DRAW)
cattr := uint32(gl.GetAttribLocation(tag.shaders, "in_c"))
gl.EnableVertexAttribArray(cattr)
gl.VertexAttribPointer(cattr, 4, gl.FLOAT, false, 0, 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(tag.faces)), gl.Pointer(&(tag.faces[0])), gl.STATIC_DRAW)
// set some state that doesn't need to change during drawing.
gl.ClearColor(0.0, 0.0, 0.0, 1.0)
gl.Enable(gl.CULL_FACE)
gl.CullFace(gl.BACK)
}