Re: Simple Test Program issues

Thank you both for your replies. I apologize if i haven't responded with a
solution yet. Quite a busy work week. In any case I will do my best to
report in over the weekend with my findings.

Again thanks!
Gerald

On Tue, May 1, 2012 at 8:33 AM, Alejandro Segovia <[email protected]> wrote:

> Hello Gerald,
>
> 2012/4/28 Gerald Escobar <[email protected]>
>
>> Hello,
>>
>> I'm trying to learn to use pyopengl in a more modern context (not relying
>> on fixed function/deprecated functionality INCLUDING built-in vertex shader
>> attributes)
>>
>> Here is my source:
>> http://pastebin.com/fd7KQthA
>>
>> When I run the program I simply get a black screen instead of a white
>> triangle.
>>
>> I'm not entirely sure what I am doing wrong however there I encountered
>> quite a few problems whilst writing this code snippet
>> 1) When trying to bind the buffer to an attribute I kept getting some
>> sort of type error. So instead I resorted to passing the matrix straight
>> 2) I'm not entirely sure about whether I'm multiplying the matricies
>> correctly.
>>
>> I apologize if this question seems very broad,
>>
>
> About 1), it's hard to be able to tell without seeing the error message
> and what line actually generates it.
>
> Regarding 2), this is for the most part a numpy thing, which I think seems
> correct :)
>
> Other than that, I see a couple of potential problems in your code. You
> are using an Identity as the projection matrix, yet you seem to supply your
> triangle coordinates in pixels. This is a semantics issue. When using an
> Identity as the projection matrix, you are asking OpenGL to render using
> device normalized coordinates. These span from [-1,-1] to [1,1], where
> these points (-1,-1) denote the lower-left corner of the screen and (1,1)
> the top-right corner. If you want to use pixels, you should create an
> Orthogonal projection matrix with left and bottom zero and right and top
> width and height (in pixels) respectively.
>
> Also, OpenGL matrices are column-major. Make sure you transpose your
> matrices when supplying them to your shader.
>
> Hope this helps,
> Alejandro.-
>
>
>
>
>>
>>
>>
>>
>>
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>
>
> --
> http://alejandrosegovia.net
>
>


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