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Re: [Public WebGL] WebGL rendering text and other basic objects



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-Ken

On Sat, Jul 9, 2011 at 9:00 PM, 吴玉宝 <wuyubao5@gmail.com> wrote:
>
> Hi, I am programming a tree-ring view for information visualization.
> First, I have drawn many ring sectors. Each sector are formed by
> triangles. They are drawn in 2D, with all vertices' Z coordinates
> equal to constant value. Each sector has a uniform color, maybe
> different from other sectors. All sectors are rendered in the same
> unique canvas.
> The vertex shader is:
>
> vColor = aVertexColor;
>
> Then, I want to render some text on each sector, which is the label of
> the sector. I have learnt how to render text through the link:
>
> http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=283502
>
> but, I saw that it need to change the fragment shader to:
>
> gl_FragColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
>
> So, if I change to this shader, I may can not render the original
> shader to a unique color, since text render need texture to assign
> color.
> Can I write two shaders, one for render the sectors, the other for
> render the texts.
> Do I need two canvas to do this? If so, does one canvas will hide the other one?
>
> Thanks,
> Yubao Wu
>
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