OpenGL ES 2 C++, Draw two Object

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Hi,
Another question : ^^

How do I draw two object in OpenGL ES 2?
For example, I need to draw Triangle and Rectangle in which solid Triangle is overlapped by transparent Rectangle.

Thanks in advance

Posted 23-Apr-12 15:43pm

satrio_budidharmawan

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Richard MacCutchan 24-Apr-12 3:48am

Draw the triangle, fill it with the solid colour, then draw the rectangle on top.

Amar Tivari 25-Apr-12 2:21am

Add alpha component in the "glcolor4f" for coloring rectangle. 0 is completly transparent and 1 is opaque

satrio_budidharmawan 25-Apr-12 2:36am

No,
glcolor4f and it's like is not recognize anymore in OpenGLES 2

2 solutions

Solution 1

Not sure if you mean this, but, referring to your previous post about the rainbow triangle, you basically do this:

C++

glVertexAttribPointer(attPosition, 3, GL_FLOAT, GL_FALSE, 0, vVertices);
glVertexAttribPointer(attColor, 4, GL_FLOAT, GL_FALSE, 0, warna);

with a different set of vertices and colors.

Posted 23-Apr-12 21:50pm

Code-o-mat

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satrio_budidharmawan 24-Apr-12 4:02am

Oh yes, I have solved it though so.
But I have another question,
How to make rectangle i created become tranparent (using GL_BLEND i think).
But nothing happened.
How's that?
Thanks

Code-o-mat 24-Apr-12 4:15am

I think you have to handle blending in the pixel shader, or fragment shader or what's the term for that in OpenGL.

satrio_budidharmawan 24-Apr-12 4:19am

here's the code line
glEnable (GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_SRC_ALPHA);

I'm not sure abaout which enum (in glBlendFunc) should i use to make my blue rectangle transparent

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satrio_budidharmawan · Accepted Answer · 2012-04-24T16:42:00

Solution 2

Next time I'll post the solution

Posted 24-Apr-12 16:42pm

satrio_budidharmawan