Question

I have written a class that currently allows the loading of 3D Models via an array and a variable(specifying the amount of variables in the array). The code seems fine to me but doesn’t draw anything on the screen.

This is the Vertex Struct.

typedef struct
{
    float pos[3];
    float texCoord[2];
    float colour[4];
} Vertex;

This is the how the Model is initialised.

- (id)VModelWithArray:(Vertex[])Vertices count:(unsigned short)count
{
    self.Vertices = Vertices;
    self.count = count;
    return self;
}

The two class variables are declared in the header like so.

@property (nonatomic, assign) Vertex *Vertices;
@property (nonatomic, assign) unsigned short count;

It is called in my view controller like so.

Vertex array[] = {
        {{1, -1, 0}, {1, 0}, {1, 0, 0, 1}},
        {{1, 1, 0}, {1, 1}, {0, 1, 0, 1}},
        {{-1, 1, 0}, {0, 1}, {1, 1, 1, 1}}
    };

    unsigned short elements = sizeof(array)/sizeof(Vertex);
    self.model = [[VModel alloc] VModelWithArray:array count:elements];

The Model class is declared in the header like so.

@property (strong, nonatomic) VModel *model;

The VBOs are created by this method.

- (void)CreateVBO
{
    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex)*self.count, self.Vertices, GL_STATIC_DRAW);
}

It is called after the Model is initialised in the view controller like so.

[self.model CreateVBO];

The Model is rendered by this method.

- (void)Render
{
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, pos));
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, texCoord));
    glEnableVertexAttribArray(GLKVertexAttribColor);
    glVertexAttribPointer(GLKVertexAttribColor, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, colour));
    glDrawArrays(GL_TRIANGLES, 0, self.count);
    glDisableVertexAttribArray(GLKVertexAttribPosition);
    glDisableVertexAttribArray(GLKVertexAttribTexCoord0);
    glDisableVertexAttribArray(GLKVertexAttribColor);
}

It is called in this method.

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect 
{
    glClearColor(0.5, 0.5, 0.5, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);
    [self.effect prepareToDraw];
    [self.model Render];
}

Any help would be very much appreciated.

Answer 1

I figured it out, I accidentally left out these lines when merging the code from a previous project.

[EAGLContext setCurrentContext:self.context];
self.effect = [[GLKBaseEffect alloc] init];