Shader doesn't work - OpenGL ES - objective-c

Question

I have created a program that allows me to display 3D objects and now I want to make a cut in relation to another object. Here is my result : screen.
The screen shows that we can see through the cut portion. So I decided to use a shader to fill this cut part.
I tried to load a shader and then to use it in a glUniform3f but that doesn't work. I did several searches on the internet, without results.
Here is my class to load a shader:
- (id)initWithVertexShaderFilename:(NSString *)vShaderFilename
fragmentShaderFilename:(NSString *)fShaderFilename
{
NSLog(fShaderFilename);
if (self = [super init])
{
attributes = [[NSMutableArray alloc] init];
NSString *vertShaderPathname, *fragShaderPathname;
program = glCreateProgram();
vertShaderPathname =[[NSBundle mainBundle]
pathForResource:vShaderFilename
ofType:#"vsh"
inDirectory:#"Shader"];
if (![self compileShader:&vertShader
type:GL_VERTEX_SHADER
file:vertShaderPathname])
NSLog(#"Failed to compile vertex shader");
else
NSLog(#"Vertex Shader OK");
fragShaderPathname = [[NSBundle mainBundle]
pathForResource:fShaderFilename
ofType:#"fsh"
inDirectory:#"Shader"];
if (![self compileShader:&fragShader
type:GL_FRAGMENT_SHADER
file:fragShaderPathname])
NSLog(#"Failed to compile fragment shader");
else
NSLog(#"Fragment shader OK");
glAttachShader(program, vertShader);
glAttachShader(program, fragShader);
}
return self;
}
- (BOOL)compileShader:(GLuint *)shader
type:(GLenum)type
file:(NSString *)file
{
NSLog(#"bonjour");
GLint status;
const GLchar *source;
source =
(GLchar *)[[NSString stringWithContentsOfFile:file
encoding:NSUTF8StringEncoding
error:nil] UTF8String];
if (!source)
{
NSLog(#"Failed to load vertex shader");
return NO;
}
*shader = glCreateShader(type);
glShaderSource(*shader, 1, &source, NULL);
glCompileShader(*shader);
glGetShaderiv(*shader, GL_COMPILE_STATUS, &status);
NSString *intString = [NSString stringWithFormat:#"%d", status];
return status = GL_TRUE;
}
#pragma mark -
- (void)addAttribute:(NSString *)attributeName
{
if (![attributes containsObject:attributeName])
{
[attributes addObject:attributeName];
glBindAttribLocation(program,
[attributes indexOfObject:attributeName],
[attributeName UTF8String]);
}
}
- (GLuint)attributeIndex:(NSString *)attributeName
{
return [attributes indexOfObject:attributeName];
}
- (GLuint)uniformIndex:(NSString *)uniformName
{
return glGetUniformLocation(program, [uniformName UTF8String]);
}
#pragma mark -
- (BOOL)link
{
GLint status;
glLinkProgram(program);
glValidateProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &status);
if (status == GL_FALSE)
return NO;
if (vertShader)
glDeleteShader(vertShader);
if (fragShader)
glDeleteShader(fragShader);
return YES;
}
- (void)use
{
glUseProgram(program);
}
Here is the function to initialize my shaders in the main class:
- (void)setup
{
GLShader *theProgram = [[GLShader alloc] initWithVertexShaderFilename:#"shader"
fragmentShaderFilename:#"shader"];
self.program = theProgram;
[self.program addAttribute:#"position"];
[self.program addAttribute:#"textureCoordinates"];
if (![self.program link])
{
NSLog(#"Link failed");
NSString *progLog = [self.program programLog];
NSLog(#"Program Log: %#", progLog);
NSString *fragLog = [self.program fragmentShaderLog];
NSLog(#"Frag Log: %#", fragLog);
NSString *vertLog = [self.program vertexShaderLog];
NSLog(#"Vert Log: %#", vertLog);
//[(GLView *)self.view stopAnimation];
self.program = nil;
}
textureCoordinateAttribute = [program attributeIndex:#"textureCoordinates"];
colorUniform = [program uniformIndex:#"uColor"];
textureUniform = [program uniformIndex:#"texture"];
//colorUniform = glGetUniformLocation(self.program, "uColor");
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ZERO);
}
Here is the function where I want to use my shader:
-(void) draw
{
[self.program use];
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glDepthMask(true);
lUniform3f(colorUniform,1.0, 1.0, 0.5);
[self drawSubtraction:image1 with:image2];
}
Here is my fragment shader:
precision highp float;
uniform vec3 uColor;
uniform vec3 uLight;
varying vec3 vNormal;
const float alpha = 0.7;
void main(void) {
float val = dot( vNormal, uLight ) * 0.4 + 0.6;
gl_FragColor = vec4( uColor * val, alpha);
}
Am I doing something wrong ? Someone has an idea that could help me ?
Thanks.

Answer 1

Your shader code looks ok. Make sure you are passing in the "textureCoordinates" attribute correctly to the vertex shader. You will need to call glEnableVertexAttribArray() and glVertexAttribPointer() at some point of the initialization. Depending on how you are rendering the models you might need to ensure you are passing in vertices correctly as well.
Also i'm assuming [self drawSubtraction:image1 with:image2] calls glDrawArrays() or glDrawElements() at some point.
The Xcode default OpenGL game project is a great place to start for loading shaders too if you want a project to compare against.