Question

I have enjoyed learning to use OpenGL under the context of games programming, and I have experimented with creating small shapes. I’m wondering if there are any resources or apps that will generate code similar to the following with a simple paint-like interface.

glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINE_STRIP);
glVertex2f(1, 0);
glVertex2f(2, 3);
glVertex2f(4, 5);
glEnd();

I’m having trouble thinking of the correct dimensions to generate shapes and coming up with the correct co-ordinates.

To clarify, I’m not looking for a program I can just freely draw stuff in and expect it to create good code to use. Just more of a visual way of representing and modifying the sets of coordinates that you need.

I solved this to a degree by drawing a shape in paint and measuring the distances between the pixels relative to a single point, but it’s not that elegant.

Answer 1

It sounds like you are looking for a way to import 2d geometry into your application. The best approach in my opinion would be to develop a content pipeline. It goes something like this:

1. You would create your content in a 3d modeling program like Google’s Sketchup. In your case you would draw 2d shapes using polygons.

2. You need a conversion tool to get the data out of the original format and into a format that your target application can understand. One way to get polygon and vertex data out of Sketchup is to export to Collada and have your tool read and process it. (The simplest format would be a list of triangles or lines.)

3. Write a geometry loader in your code that reads the data created by your conversion tool. You need to write opengl code that uses vertex arrays to display the geometry.