Opengl Es 2.0 Sphere

How to draw a sphere in OpenGL ES 2 correctly

"I was wondering what the difference between gldrawarrays and gldrawelements is?"

glDrawArrays is used when you deal directly with a stream of vertices, and glDrawElements is used when you use an index buffer, which adds an extra layer of indirection and lets you reference vertices by an index number. You can check out this article for more info on glDrawElements (disclaimer: I wrote the article): http://www.learnopengles.com/android-lesson-eight-an-introduction-to-index-buffer-objects-ibos/

The OpenGL ES manual also has info about these two functions:

http://www.khronos.org/opengles/sdk/docs/man/xhtml/glDrawArrays.xml
http://www.khronos.org/opengles/sdk/docs/man/xhtml/glDrawElements.xml

"Another question i have is how to draw a sphere for the android."

You essentially just have to break it down into triangles. One simple way of doing this is tesselating the sphere using latitude and longitude, like the lines on a globe. You can use a loop with sin and cos to generate the points.

These two questions on Stack Overflow have some example code that should be straightforward to adapt to Android:

• Creating a 3D sphere in Opengl using Visual C++
• calculating a sphere in opengl

Drawing a sphere in OpenGL ES 2.0

You're setting vertexCount as lat * lon * bytes per float, which looks very weird to me.

I think you have misnamed this variable, as the number of vertices has nothing to do with bytes per float.

You're using the same variable in glDrawArrays, which seems to me will not have the accurate number of vertices.

Android OpenGL ES 2.0: Sphere Texture Mapping

I can see at least one thing which seems to be wrong...

GLES20.glVertexAttribPointer(textureCoordHandle, 3,
        GLES20.GL_FLOAT, false, 0, ufo_sphere.getTexCoords());

Texture coordinates typically have a size of 2 (u, v). So you could try this instead:

GLES20.glVertexAttribPointer(textureCoordHandle, 2,
        GLES20.GL_FLOAT, false, 0, ufo_sphere.getTexCoords());

Also, in the link you provided they use the GL_TRIANGLES format instead of GL_TRIANGLE_STRIP so you should switch back to that.

OpenGL ES 2.0: Filling in a Sphere instead of it being wireframe

It looks like you are calculating vertex indices in your setup code, but not using them. Consider using glDrawElements instead of glDrawArrays.

It also looks like you are half way between using GL_TRIANGLE_STRIP (one new index per triangle after the first triangle) and GL_TRIANGLES (three indices per triangle). You will probably find it easier to use GL_TRIANGLES.

How to draw and texture a UV Sphere with OpenGL 2.0 for Android

Ok, the problem is solved now. The textures were not working properly because the generated point indices start at 1 instead of 0. By substracting 1 to all indices the problem is solved... :)

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