Pass additional N textures to a custom shader in cocos2d - c++11

Question

I want to pass N number of texture to a custom shader. As I surfed thru net, the best option I've got is to override the Sprite::draw() function and add a CustomCommand object to the draw pool.
CPP file:
void SpriteSub::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags) {
m_cmdCustom.init(_globalZOrder, transform, flags);
m_cmdCustom.func = CC_CALLBACK_0(SpriteSub::onDraw, this, transform, flags);
renderer->addCommand(&m_cmdCustom);
Sprite::draw(renderer, transform, flags);
}
void SpriteSub::onDraw(const Mat4 &transform, uint32_t /*flags*/) {
this->getGLProgram()->use();
auto wwProgram = m_shader->getProgram();
auto texBall0 = Director::getInstance()->getTextureCache()->addImage("ball.png")->getName();
GLuint locTexIcon0 = glGetUniformLocation(wwProgram, "texBall0");
glUniform1i(locTexIcon0, 0);
//glActiveTexture(GL_TEXTURE0 + 0); glBindTexture(GL_TEXTURE_2D, texBall0);
//glActiveTexture(GL_TEXTURE0 + 0);
GL::bindTexture2D(texBall0);
}
frament shader:
#ifdef GL_ES
precision lowp float;
#endif
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
uniform sampler2D texBall0;
uniform sampler2D texBall1;
//uniform sampler2D texBall2;
//uniform sampler2D texBall3;
//uniform sampler2D texBall4;
//uniform sampler2D texBall5;
void main()
{
float t = 0.7f;
//gl_FragColor = texture2D(CC_Texture0, v_texCoord);
//this is just a sample code
gl_FragColor = texture2D(texBall0, v_texCoord) * t;
gl_FragColor += texture2D(texBall1, v_texCoord) * (t-1);
//some code that uses the other textures...
}
The shader above is just a sample and not the actual code I'm using. For now, I just need to successfully pass multiple textures in a single shader to process their pixels.
Currently, I can't display the passed texture. What should be done to achieve this? Does Sprite::draw() in SpriteSub::draw() cancel-out the gl commands from onDraw()?

Answer 1

'Solved it!
You don't even need to override the draw or add a CustomCommand to render queue.
Steps:
1.) Create a GLProgramState with the GLProgram object you created with your custom shaders.
2.) Use GLProgramState::setUniformTexture("uniformVarName", tex2D) to locate uniform variable and pass texture name.
3.) Call sprite->setGLProgramState(programState) instead of sprite->setGLProgram(program);
CCP File:
m_shader = GLProgram::createWithByteArrays(ccPositionTextureColor_noMVP_vert, shader_frag);
m_shader->retain();
auto shaderState = GLProgramState::getOrCreateWithGLProgram(m_shader);
auto textureCache = Director::getInstance()->getTextureCache();
auto img0 = textureCache->addImage("icon_tex0.png")->getName();
auto img1 = textureCache->addImage("icon_tex1.png")->getName();
auto img2 = textureCache->addImage("icon_tex2.png")->getName();
auto img3 = textureCache->addImage("icon_tex3.png")->getName();
auto img4 = textureCache->addImage("icon_tex4.png")->getName();
auto img5 = textureCache->addImage("icon_tex5.png")->getName();
shaderState->setUniformTexture("texIcon0", img0);
shaderState->setUniformTexture("texIcon1", img1);
shaderState->setUniformTexture("texIcon2", img2);
shaderState->setUniformTexture("texIcon3", img3);
shaderState->setUniformTexture("texIcon4", img4);
shaderState->setUniformTexture("texIcon5", img5);
//this->setGLProgram(m_shader);
this->setGLProgramState(shaderState);
fragment shader:
#ifdef GL_ES
precision lowp float;
#endif
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
uniform sampler2D texIcon0;
uniform sampler2D texIcon1;
uniform sampler2D texIcon2;
uniform sampler2D texIcon3;
uniform sampler2D texIcon4;
uniform sampler2D texIcon5;
void main()
{
int numTex = 6;
float fWeight = 1.0f/float(length);
//gl_FragColor = texture2D(CC_Texture0, v_texCoord);
gl_FragColor += texture2D(texIcon0, v_texCoord) * fWeight;
gl_FragColor += texture2D(texIcon1, v_texCoord) * fWeight;
gl_FragColor += texture2D(texIcon2, v_texCoord) * fWeight;
gl_FragColor += texture2D(texIcon3, v_texCoord) * fWeight;
gl_FragColor += texture2D(texIcon4, v_texCoord) * fWeight;
gl_FragColor += texture2D(texIcon5, v_texCoord) * fWeight;
}
sources:
http://discuss.cocos2d-x.org/t/solved-passing-a-variable-to-a-shader/27141/3
http://cocos2d-x.org/docs/programmers-guide/advanced_topics/index.html#customizing-shaders