If you're learning OpenGL ES on Android, the first thing everyone tries is drawing a triangle.
And yet…
👉 You either get a black screen
👉 Or nothing shows up
👉 Or the app crashes without explanation
In this guide, I’ll show you exactly how to draw a triangle in OpenGL ES, with working code and common mistakes to avoid.
What You’ll Learn Here
- How OpenGL ES rendering works (basic idea)
- How to define triangle vertices
- How shaders work (simple explanation)
- Working Android code to render a triangle
Step 1: Define Triangle Coordinates
float triangleCoords[] = {
0.0f, 0.5f, 0.0f, // top
-0.5f, -0.5f, 0.0f, // bottom left
0.5f, -0.5f, 0.0f // bottom right
};
👉 This defines a triangle in 3D space (x, y, z)
Step 2: Create Vertex Shader
String vertexShaderCode =
"attribute vec4 vPosition;" +
"void main() {" +
" gl_Position = vPosition;" +
"}";
👉 This shader tells OpenGL where to place the triangle
Step 3: Create Fragment Shader
String fragmentShaderCode =
"precision mediump float;" +
"void main() {" +
" gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);" +
"}";
👉 This makes the triangle red
Step 4: Draw the Triangle
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
🖼️ Output
👉 You should now see a red triangle centered on screen
Common Mistakes (IMPORTANT)
1. Black Screen
-
Forgot to call
glClear() - Shader failed to compile
2. Triangle Not Visible
- Coordinates out of range (-1 to +1)
- Wrong buffer setup
3. App Crash
- Missing OpenGL context
- Incorrect shader linking
Pro Tip
If nothing shows:
👉 Always check shader compile logs — 90% of errors are there.
What Next?
Now that you can draw a triangle, try:
- Drawing a square
- Adding colors per vertex
- Animating the triangle
Final Thoughts
This may look simple, but this triangle is the foundation of all 3D graphics—games, simulations, everything.
