Basic Render-to-Texture

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Cower	Created : 09 April 2010 System : Cross Platform Language : Blitz Max Basic Render-to-Texture Very simple render-to-texture classes for OpenGL
This is a set of very simple classes for render-to-texture in OpenGL. Made this mainly to get an idea of how to do it, and I don't expect this is the optimal way of doing things. Might prove useful if you want to get a quick idea of how to do it, though. ' rtt.bmx SuperStrict Import Brl.Graphics Import Pub.Glew Global NullRenderBuffer:RenderBuffer = New RenderBuffer Global NullFrameBuffer:FrameBuffer = New FrameBuffer Type FrameBuffer Field seq:Int Field _buffer:Int=0 Method Init:FrameBuffer() Assert _buffer=0 seq = GraphicsSeq glGenFramebuffers(1, Varptr _buffer) Return Self End Method Method Dispose() If _buffer <> 0 And seq = GraphicsSeq Then glDeleteFramebuffers(1, Varptr _buffer) EndIf _buffer = 0 End Method Method Delete() Dispose() End Method Method Bind(target%) glBindFramebuffer(target, _buffer) End Method Method Buffer:Int() Return _buffer End Method End Type Type RenderBuffer Field seq:Int Field _buffer:Int=0 Method Init:RenderBuffer() Assert _buffer=0 seq = GraphicsSeq glGenRenderbuffers(1, Varptr _buffer) Return Self End Method Method Dispose() If _buffer <> 0 And seq = GraphicsSeq Then glDeleteRenderbuffers(1, Varptr _buffer) EndIf _buffer = 0 End Method Method Delete() Dispose() End Method Method Bind() glBindRenderbuffer(GL_RENDERBUFFER, _buffer) End Method Method Buffer:Int() Return _buffer End Method End Type Type RenderTexture Field seq:Int Field fbo:FrameBuffer = New FrameBuffer Field depth:RenderBuffer = New RenderBuffer Field tex:Int Field _mipt:Int Method InitWithSize:RenderTexture(width%, height%) Assert tex=0 Local prevFBO%, prevTex%, prevRBO%, prevTex2D% glGetIntegerv(GL_RENDERBUFFER_BINDING, Varptr prevRBO) glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, Varptr prevFBO) glGetIntegerv(GL_TEXTURE_BINDING_2D, Varptr prevFBO) glGetIntegerv(GL_TEXTURE_2D, Varptr prevTex2D) If prevTex2D = 0 Then glEnable(GL_TEXTURE_2D) EndIf fbo = fbo.Init() glGenTextures(1, Varptr tex) fbo.Bind(GL_DRAW_FRAMEBUFFER) glBindTexture(GL_TEXTURE_2D, tex) glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, Null) glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0) depth = depth.Init() depth.Bind() glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, width, height) glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth.Buffer()) glBindRenderbuffer(GL_RENDERBUFFER, prevRBO) glBindFramebuffer(GL_DRAW_FRAMEBUFFER, prevFBO) glBindTexture(GL_TEXTURE_2D, prevTex) If prevTex2D = 0 Then glDisable(GL_TEXTURE_2D) EndIf seq = GraphicsSeq Return Self End Method Method Dispose() fbo.Dispose() depth.Dispose() If tex <> 0 And seq = GraphicsSeq Then glDeleteTextures(1, Varptr tex) EndIf tex = 0 _mipt = False End Method Method Delete() Dispose() End Method Method Bind() glBindTexture(GL_TEXTURE_2D, tex) glGenerateMipmap(GL_TEXTURE_2D) _mipt = True End Method Method SetFramebuffer() glBindTexture(GL_TEXTURE_2D, 0) fbo.Bind(GL_DRAW_FRAMEBUFFER) _mipt = False End Method End Type --v For a short example that's probably considered a crime against humanity in a few US states: SuperStrict Import "rtt.bmx" Import Brl.GlGraphics SetGraphicsDriver(GLGraphicsDriver()) Local gfx:TGraphics = Graphics(800, 600, 0) glewInit() ' Projection matrices Local screenProj:Float[16] Local rttProj:Float[16] ' Set up GL state glEnable(GL_TEXTURE_2D) ' Create screen/texture projection matrices glMatrixMode(GL_PROJECTION) glLoadIdentity() glOrtho(0, 1024, 0, 768, -20, 20) glGetFloatv(GL_PROJECTION_MATRIX, screenProj) glLoadIdentity() glOrtho(0, 256, 0, 256, -20, 20) glGetFloatv(GL_PROJECTION_MATRIX, rttProj) ' Create RTT texture Local rt:RenderTexture = New RenderTexture.InitWithSize(128, 128) While Not AppTerminate() ' Draw to texture rt.SetFramebuffer() glViewport(0, 0, 128, 128) glClearColor(1, 1, 1, 1) glClear(GL_COLOR_BUFFER_BIT \| GL_DEPTH_BUFFER_BIT) glMatrixMode(GL_PROJECTION) glLoadMatrixf(rttProj) glMatrixMode(GL_MODELVIEW) glLoadIdentity() ' Animate the texture a bit Local t!=Millisecs().05! glTranslatef(128+64Sin(t), 128+64*Cos(t), 0) glRotatef(t, 0, 0, 1) glTranslatef(-32, -32, 0) ' Draw a red something glBegin(GL_POLYGON) glColor3f(1,0,0) glVertex2f(0, 0) glVertex2f(0, 64) glVertex2f(64, 64) glVertex2f(64, 0) glEnd() ' Draw to window NullFrameBuffer.Bind(GL_DRAW_FRAMEBUFFER) glViewport(0, 0, GraphicsWidth(), GraphicsHeight()) glClearColor(0, 0, 0, 1) glClear(GL_COLOR_BUFFER_BIT \| GL_DEPTH_BUFFER_BIT) glMatrixMode(GL_PROJECTION) glLoadMatrixf(screenProj) glMatrixMode(GL_MODELVIEW) glLoadIdentity() rt.Bind() ' Bind RTT texture glBegin(GL_POLYGON) glColor3f(1,1,1) glTexCoord2f(1,0) ; glVertex2f(0, 0) glTexCoord2f(0,0) ; glVertex2f(0, 512) glTexCoord2f(0,1) ; glVertex2f(512, 512) glTexCoord2f(1,1) ; glVertex2f(512, 0) glEnd() Flip() Wend rt.Dispose() --v

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