Question

I am trying to adapt this tutorial about shaders to work in my game and later I am going to mess with glsl to get the desired effect I want.

I created a Cocos2d 2.x project with Box2D. The Box2D template gives me a PhysicsSprite class which is why I don’t use CCSprite. Here is my init method:

-(id) init
{
    if( (self=[super init])) {

        s = [[CCDirector sharedDirector] winSize];

        // enable events

        self.isTouchEnabled = YES;
        self.isAccelerometerEnabled = YES;

        // init physics
        [self initPhysics];

        //Init shader effects.
        [self initShaderEffects];

        ball = [PhysicsSprite spriteWithFile:@"Ball.png"];
        ball.position = ccp(s.width/2, s.height/2);
        b_body = [self createCirBody:10 andSpr:ball];
        [ball setPhysicsBody:b_body];
        [self addChild:ball];

        b_body->SetLinearVelocity(b2Vec2(1.5f,0));

        [self scheduleUpdate];
    }
    return self;
}

If you exclude the [self initShaderEffects]; line I have tested the code, it works so far, I get a moving ball. Here is my initShaderEffects (which is essentially the same as the tutorials except I use ball instead of sprite and I changed the fragmentSource initialization to use a non-deprecated method):

-(void)initShaderEffects {
    const GLchar *fragmentSource = (GLchar*)[[NSString stringWithContentsOfFile:@"MyCustomShader.fsh" encoding:NSUTF8StringEncoding error:nil] UTF8String];
    ball.shaderProgram = [[CCGLProgram alloc] initWithVertexShaderByteArray:ccPositionTextureA8Color_vert fragmentShaderByteArray:fragmentSource];
    [ball.shaderProgram addAttribute:kCCAttributeNamePosition index:kCCVertexAttrib_Position];
    [ball.shaderProgram addAttribute:kCCAttributeNameTexCoord index:kCCVertexAttrib_TexCoords];
    [ball.shaderProgram link];
    [ball.shaderProgram updateUniforms];

    colorRampUniformLocation = glGetUniformLocation(ball.shaderProgram->program_, "u_colorRampTexture"); //EXC_BAD_ACCESS
    glUniform1i(colorRampUniformLocation, 1);

    colorRampTexture = [[CCTextureCache sharedTextureCache] addImage:@"x2.png"];
    [colorRampTexture setAliasTexParameters];

    [ball.shaderProgram use];
    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, [colorRampTexture name]);
    glActiveTexture(GL_TEXTURE0);

}

And lastly here is my shader “MyCustomShader.fsh” copied straight from the tutorial:

#ifdef GL_ES
precision mediump float;
#endif

// 1
varying vec2 v_texCoord;
uniform sampler2D u_texture;
uniform sampler2D u_colorRampTexture;

void main()
{ // 2
    vec3 normalColor = texture2D(u_texture, v_texCoord).rgb;

    // 3
    float rampedR = texture2D(u_colorRampTexture, vec2(normalColor.r, 0)).r;
    float rampedG = texture2D(u_colorRampTexture, vec2(normalColor.g, 0)).g;
    float rampedB = texture2D(u_colorRampTexture, vec2(normalColor.b, 0)).b;

    // 4
    gl_FragColor = vec4(rampedR, rampedG, rampedB, 1);
}

This code gives me EXC_BAD_ACCESS on the line I have comment EXC_BAD_ACCESS on in my initShaderEffects method. I find shaders difficult and it would be much appreciated if someone could tell me where am I going wrong.

Answer 1

Please ensure that “MyCustomShader.fsh” is added to “Copy Boundle Resources” section in “Project target” => “Build phases”. If it doesn’t help check values of fragmentSource and ball.shaderProgram in debugger.

I found another issue in your code: initShaderEffects executed before “ball” creation. You should move line with “[self initShaderEffects];” after line “[self addChild:ball];”.