CODEWITHSUNDEEP
opengl-esios6opengl-es-2.0game-physicsglkit
Er. Mayur Sharma
Er. Mayur Sharma

Reputation: 93

How do I get a cube having different textured image on each face of cube in glkit?

I am developing a game in which I have to shake a dice to get number. I am using glkit to make a cube and texturing that cube by GLKBaseEffect. Well ! I want a cube having diffrent textured images on each faces so that it can simulates a dice. I want each faces of cube show different dice image like one face show number 1 another face show number two and so on.

I am pasting my code here.

- (void)setupGL {

[EAGLContext setCurrentContext:self.context];
glEnable(GL_CULL_FACE);

    
self.effect = [[GLKBaseEffect alloc] init];

NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithBool:YES],
                          GLKTextureLoaderOriginBottomLeft, 
                          nil];

NSError * error;    
NSString *path = [[NSBundle mainBundle] pathForResource:@"tile_floor" ofType:@"png"];
GLKTextureInfo * info = [GLKTextureLoader textureWithContentsOfFile:path options:options error:&error];
if (info == nil) {
    NSLog(@"Error loading file: %@", [error localizedDescription]);
}
self.effect.texture2d0.name = info.name;
self.effect.texture2d0.enabled = true;

// draw one texture per side



// New lines
glGenVertexArraysOES(1, &_vertexArray);
glBindVertexArrayOES(_vertexArray);

// Old stuff
glGenBuffers(1, &_vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);

glGenBuffers(1, &_indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);

// New lines (were previously in draw)
glEnableVertexAttribArray(GLKVertexAttribPosition);        
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Position));
glEnableVertexAttribArray(GLKVertexAttribColor);
glVertexAttribPointer(GLKVertexAttribColor, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Color));
glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, TexCoord));

// New line
glBindVertexArrayOES(0); 
}

and calling draw elements method from here in drawInRects

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {

glClearColor(1.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
[self.effect prepareToDraw];
glBindVertexArrayOES(_vertexArray);
glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), GL_UNSIGNED_BYTE, 0);

}

How can I achieve this?

Upvotes: 0

Views: 728

Answers (2)

Stephen Wyatt
Stephen Wyatt

Reputation: 1

I do this by layering, or having more objects. So, a cube, and then two squares that are just barely on the skin of the cube. If the cube is 2 x 2 x 2, just make the picture vertex 2.01, and so it is like cake icing

So you are not texturing the cube, you are adding more objects. Here is a video example - https://www.youtube.com/watch?v=lh2Zc8kHFbU&list=UUu5WfUbKdhLCW9aPq3WZsNA

Upvotes: 0

Olie
Olie

Reputation: 24675

GLKit has a limited number of textures allowed (2, I think), so you'll need what's called a texture-map. Basically, you set up a texture like this:

a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d ...
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d
a a a a a a a a b b b b b b b b c c c c c c c c d d d d d d d d

And then you set your texture coordinates for each vertex to point to the sub-portion of the texture that you want to use.

NOTE: Even if GLKit supported more textures, as many OpenGL implementations do, this method is MUCH faster than loading a gazillion textures and switching them all the time. glBind() is a relatively slow operation.

Also note: Things are more efficient if your texture image sides are powers of 2 (2, 4, 8, 16, 32, ...) It's ok to have blank (unused) spots in your texture image. I typically put a big red blotch in the unused part, so I can tell if it inadvertently shows up on anything.

So your dice-texture might be, say, 32px tall, and 512 (32*8) wide, but you only use the first 192 (32*6) of it and have a set of six 32x32 textures all in one image.

Upvotes: 1

Related Questions