Displaying multiple cubes in OpenGL with shaders

I'm new to OpenGL and shaders. I have a project that involves using shaders to display cubes.

So basically I'm supposed to display eight cubes using a perspective projection at (+-10,+-10,+-10) from the origin each in a different color. In other words, there would be a cube centered at (10, 10, 10), another centered at (10, 10, -10) and so on. There are 8 combinatio开发者_运维技巧ns in (+-10, +-10, +-10). And then I'm supposed to provide a key command 'c' that changes the color of all the cubes each time the key is pressed.

So far I was able to make one cube at the origin. I know I should use this cube and translate it to create the eight cubes but I'm not sure how I would do that. Does anyone know how I would go about with this?

That question is, as mentioned, too broad. But you said that you managed to draw one cube so I can assume that you can set up camera and your window. That leaves us whit how to render 8 cubes. There are many ways to do this, but I'll mention 2 very different ones.

Classic: You make function that takes 2 parameters - center of cube, and size. Whit these 2 you can build up cube the same way you're doing it now, but instead of fixed values you will use those variables. For example, front face would be:

glBegin(GL_TRIANGLE_STRIP);
glVertex3f(center.x-size/2, center.y-size/2, center.z+size/2);
glVertex3f(center.x+size/2, center.y-size/2, center.z+size/2);
glVertex3f(center.x-size/2, center.y+size/2, center.z+size/2);
glVertex3f(center.x+size/2, center.y+size/2, center.z+size/2);
glEnd();

This is just for showcase how to make it from variables, you can do it the same way you're doing it now.

Now, you mentioned you want to use shaders. Shader topic is very broad, just like openGL itself, but I can tell you the idea. In openGL 3.2 special shaders called geometry were added. Their purpose is to work with geometry as whole - on contrary that vertex shaders works whit just 1 vertex at time or that fragment shaders work just whit one fragment at time - geometry shaders work whit one geometry piece at time. If you're rendering triangles, you get all info about single triangle that is just passing through shaders. This wouldn't be anything serious, but these shaders doesn't only modify these geometries, they can create new ones! So I'm doing in one of my shader programs, where I render points, but when they pass through geometry shader, these points are converted to circles. Similarly you can render just points, but inside geometry shader you can render whole cubes. The point position would work as center for these cubes and you should pass size of cubes in uniform. If size of cubes may vary, you need to make vertex shader also that will pass the size from attribute to variable, which can be read in geometry shader.

As for color problem, if you don't implement fragment shaders, only thing you need to do is call glColor3f before rendering cubes. It takes 3 parameters - red, green and blue values. Note that these values doesn't range from 0 to 255, but from 0 to 1. You can get confused that you cubes aren't rendered if you use white background and think that when you set colors to 200,10,10 you should see red cubes but you don't see anything. That's because in fact you render white cubes. To avoid such errors, I recommend to set background to something like grey whit glClearColor.