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ofxMultiXbo

github.com/bensnell/ofxMultiXbo · @bensnell
OF 0.12 Graphics Shaders

Utilities for Manipulating Multiple Buffer Objects (FBOs and PBOs)

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ammortal-inc/ofxMultiXbo by @ammortal-inc · ★ 1 · pushed 1y ago

README

ofxMultiXbo

Utilities for Manipulating Multiple <u>X</u> Buffer Objects (<u>F</u>BOs and <u>P</u>BOs)

Table of Contents



Project Details Installation Usage Troubleshooting Roadmap License Notes

Project Details



There is no object called ofxMultiXbo. Rather, it represents the collection of other buffer objects, which are individually described in detail below:

ofxMultiFbo



This is a helper class for handling frame buffer objects (FBOs) with multiple texture targets. It is useful in combination with shaders that output multiple textures.

Internally, it contains two FBOs for every one allocated. These two FBOs are used to ping pong textures back and forth, so that one can be written to (the utility FBO) while the other is read from (the data FBO). Between fbo.begin() and fbo.end() calls, the texture fbo.getTex(i) contains the last rendered texture (this is analogous to fbo.getDataFbo()). After the call to fbo.end(), textures are swapped and fbo.getTex(i) contains the just-rendered texture (this is analogous to fbo.getDataFbo()).

Note: This object is limited to 8 attached buffer objects on a single ofxMultiFbo instance.

An example of usage includes:

main.cpp

Note: Your main.cpp file needs to be set up like this, enabling support for GL version 3.2

``c++ int main() {

ofGLFWWindowSettings winSettings; winSettings.setGLVersion(3, 2); winSettings.numSamples = 8; winSettings.setSize(1920, 1080);

shared_ptr<ofAppBaseWindow> win = ofCreateWindow(winSettings); // sets up the opengl context! ((ofAppGLFWWindow)win.get())->setMultiDisplayFullscreen(true);

ofRunApp(win, shared_ptr<ofBaseApp>(new ofApp())); ofRunMainLoop(); } 

ofApp.h
c++ class ofApp : public ofBaseApp { ofxMultiFbo fbo; ofShader shader; } 

ofApp.cpp
c++ ofApp::Setup() { // Allocate a frame buffer consisting of two RGBA textures // at 100 x 100 pixels initialized with the color white // and without PBO support. fbo.allocate(100, 100, GL_RGBA, 2, ofColor(255), false);

// Load Shader shader.load("shaders/myShader"); }

ofApp::Update() { // Run the shader and save its two outputs to the two texture // targets in fbo fbo.begin(); ofClear(0,0,0,0); // Clear the textures shader.begin(); shader.setUniformTexture("tex0", fbo.getTex(0), 0); shader.setUniformTexture("tex1", fbo.getTex(1), 1); fbo.getTex(0).draw(0,0); // Call the shader to run shader.end(); fbo.end(); }

ofApp::Draw() { // Draw the two just-rendered textures. fbo.getTex(0).draw(0,0,100,100); fbo.getTex(1).draw(100,0,100,100); } 

myShader.frag 

Note: Your fragment shader must have this header to specify its version and a numberof extensions required for operation. Every texture generated within ofxMultiFbo will be accessible in order as an output. The name outTex0 can be user-specified within the shader.
c

version 150

extension GL_ARB_explicit_uniform_location : enable

extension GL_ARB_explicit_attrib_location : enable



in vec2 texCoordVarying;

layout (location = 0) out vec4 outTex0; // First output texture layout (location = 1) out vec4 outTex1; // Second output texture

void main() { outTex0 = vec4(1,0,0,1); outTex1 = vecr(texCoordVarying.x/100.0,texCoordVarying.y/100.0,0,1); } 

myShader.vert

Note: You must also include the header version in the vertex shader.
c

version 150



uniform mat4 modelViewProjectionMatrix;

in vec4 position; in vec2 texcoord;

out vec2 texCoordVarying;

void main() { texCoordVarying = texcoord; gl_Position = modelViewProjectionMatrix * position; } ``

ofxMultiPbo



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Installation



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Usage



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Troubleshooting



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Roadmap



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License



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Notes



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