OpenGL ES triangle not showing - objective-c

Question

First of all I'm french so sorry for my english.
I'm new to OpenGL ES and I'm trying to draw a simple triangle with these Vertices :
typedef struct {
float Position[3];
float Color[4];
} Vertex;
const Vertex Vertices[] = {
{{0.0, 1.0, -2.0}, {1, 0, 0, 1}},
{{1.0, 0.0, -2.0}, {1, 0, 0, 1}},
{{-1.0, 0.0, -2.0}, {1, 0, 0, 1}},
};
and these indices ;
const GLubyte Indices[] = {
0,1,2
};
But the triangle is not showing up... If I change the indices to 0,2,3, It displays a triangle with vertex 0,2 and a black vertex : {{0,0,0},{0,0,0,1}} , but there is no 4th vertex... I don't understand at all could someone explain me?
Here's my Xcode view code :
//
// EAGLView.m
// OpenGlintro
//
// Created by Arnaud Miguet on 01/12/12.
// Copyright (c) 2012 Tap‘n'Develop. All rights reserved.
//
#import "EAGLView.h"
#implementation EAGLView
+ (Class) layerClass {
return [CAEAGLLayer class];
}
- (void)setupVBOs {
GLuint vertexBuffer;
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
GLuint indexBuffer;
glGenBuffers(1, &indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);
}
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
CAEAGLLayer *EAGLLayer = (CAEAGLLayer *) super.layer;
EAGLLayer.opaque = YES;
context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
if (!context || ![EAGLContext setCurrentContext:context]) {
[self release];
return nil;
}
GLuint framebuffer , renderbuffer;
glGenBuffers(1, &framebuffer);
glGenBuffers(1, &renderbuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
[context renderbufferStorage:GL_RENDERBUFFER fromDrawable:EAGLLayer];
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);
glViewport(10, 0, CGRectGetWidth(frame), CGRectGetHeight(frame));
[self compileShaders];
[self setupVBOs];
[self render];
}
return self;
}
- (void)render {
glClearColor(0, 104.0/255.0, 55.0/255.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
// 1
glViewport(0, 0, self.frame.size.width, self.frame.size.height);
// 2
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE,
sizeof(Vertex), 0);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE,
sizeof(Vertex), (GLvoid*) (sizeof(float) * 3));
// 3
glDrawElements(GL_TRIANGLES, sizeof(Indices),
GL_UNSIGNED_BYTE, 0);
[context presentRenderbuffer:GL_RENDERBUFFER];
}
- (GLuint)compileShader:(NSString*)shaderName withType:(GLenum)shaderType {
// 1
NSString* shaderPath = [[NSBundle mainBundle] pathForResource:shaderName
ofType:#"glsl"];
NSError* error;
NSString* shaderString = [NSString stringWithContentsOfFile:shaderPath
encoding:NSUTF8StringEncoding error:&error];
if (!shaderString) {
NSLog(#"Error loading shader: %#", error.localizedDescription);
exit(1);
}
// 2
GLuint shaderHandle = glCreateShader(shaderType);
// 3
const char * shaderStringUTF8 = [shaderString UTF8String];
int shaderStringLength = [shaderString length];
glShaderSource(shaderHandle, 1, &shaderStringUTF8, &shaderStringLength);
// 4
glCompileShader(shaderHandle);
// 5
GLint compileSuccess;
glGetShaderiv(shaderHandle, GL_COMPILE_STATUS, &compileSuccess);
if (compileSuccess == GL_FALSE) {
GLchar messages[256];
glGetShaderInfoLog(shaderHandle, sizeof(messages), 0, &messages[0]);
NSString *messageString = [NSString stringWithUTF8String:messages];
NSLog(#"%#", messageString);
exit(1);
}
return shaderHandle;
}
- (void)compileShaders {
// 1
GLuint vertexShader = [self compileShader:#"SimpleVertex"
withType:GL_VERTEX_SHADER];
GLuint fragmentShader = [self compileShader:#"SimpleFragment"
withType:GL_FRAGMENT_SHADER];
// 2
GLuint programHandle = glCreateProgram();
glAttachShader(programHandle, vertexShader);
glAttachShader(programHandle, fragmentShader);
glLinkProgram(programHandle);
// 3
GLint linkSuccess;
glGetProgramiv(programHandle, GL_LINK_STATUS, &linkSuccess);
if (linkSuccess == GL_FALSE) {
GLchar messages[256];
glGetProgramInfoLog(programHandle, sizeof(messages), 0, &messages[0]);
NSString *messageString = [NSString stringWithUTF8String:messages];
NSLog(#"%#", messageString);
exit(1);
}
// 4
glUseProgram(programHandle);
// 5
_positionSlot = glGetAttribLocation(programHandle, "Position");
_colorSlot = glGetAttribLocation(programHandle, "SourceColor");
glEnableVertexAttribArray(_positionSlot);
glEnableVertexAttribArray(_colorSlot);
}
typedef struct {
float Position[3];
float Color[4];
} Vertex;
const Vertex Vertices[] = {
{{0.0, 1.0, -2.0}, {1, 0, 0, 1}},
{{1.0, 0.0, -2.0}, {1, 0, 0, 1}},
{{-1.0, 0.0, -2.0}, {1, 0, 0, 1}},
};
const GLubyte Indices[] = {
0,2,3
};
#end

Answer 1

Add a vertex array before you bind the buffers.
GLuint vao;
glGenVertexArray(1, &vao);
glBindVertexArray(vao);