I think it is like glOrtho. I found this on koders.com:
public void glOrthof(float left, float right, float bottom, float top,
float near, float far) {
Matrix.orthoM(mMatrix, mTop, left, right, bottom, top, near, far);
}
I think maybe when you use glOrtho, the depth buffer stuff is backwards.
You might have to change GL_LESS to GL_GREATER using glDepthFunc or
something.
I switched one of my games to glOrtho back in the day. IIRC, I thought it
would be easy, and it turned out to be a root canal.
On Friday, September 14, 2012 4:25:39 AM UTC-5, reaktor24 wrote:
>
> Hi
>
> Thanks for your replies. So its not like the old glOrtho then? Ok, I will
> have a play with it later tonight and see how I get on. Ideally I would
> like the origin in the bottom left corner as that seems the most logical to
> me. Thanks again.
>
> Steve
>
> On Friday, September 14, 2012 10:19:45 AM UTC+1, RichardC wrote:
>
>> The nice thing about frustumM and orthoM is that they take the same
>> parameters :) They just produce different view transformations.
>>
>> The distance parameters (near and far) are the clip planes (which you
>> still have in an orthographic projection) in front of the camera position
>> (so they should both be positive).
>>
>> The other parameters control the volume of the view space projected onto
>> your graphics window and if you want the x,y origin in the centre of the
>> screen then you need to pass in -x, +x, -y, +y (for given values of x and
>> y), as your screen is not square you need to workout it's aspect ratio so
>> as to not "squash" the transformation.
>>
>>
>> On Friday, September 14, 2012 9:54:43 AM UTC+1, reaktor24 wrote:
>>>
>>> Hi Richard
>>>
>>> Thanks for your reply but I don't want to use frustumM I want to use
>>> orthoM. I want a 2D projection not 3D hence the -1 to +1. I have use
>>> frustumM and it works ok, I can see the triangle. What is the negative
>>> aspect ratio about? I don't understand that. It should really work like the
>>> old glOrtho function but I guess it doesn't which is a shame.
>>>
>>> Steve
>>>
>>> On Friday, September 14, 2012 9:46:58 AM UTC+1, RichardC wrote:
>>>
>>>> See:
>>>>
>>>> android-sdk\samples\android-10\ApiDemos\src\com\example\android\apis\graphics\GLES20TriangleRenderer.java
>>>>
>>>> for Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
>>>>
>>>> which is similar.
>>>>
>>>> There is a lot of information out there on OpenGL projections,
>>>> I suggest you read some of it.
>>>>
>>>> Note that:
>>>> * near and far should both be +ve as they are distances in front of the
>>>> camera in the direction the camera is looking.
>>>> * if your triangle is at 0 on the z-axis you will need to move your
>>>> camera position (which defaults to [0,0,0]) so you can see it.
>>>>
>>>>
>>>> On Friday, September 14, 2012 9:27:35 AM UTC+1, reaktor24 wrote:
>>>>>
>>>>> I have a very simple application which draws a triangle at zero on the
>>>>> z axis. I want an orthographics view but for the life of me this
>>>>> function won't work. It just shows a black screen with no triangle.
>>>>> How exactly do you use this function? I did the obvious thing which
>>>>> is:
>>>>>
>>>>> Matrix.orthoM(projection,0,0,width,0,height,-1,1);
>>>>>
>>>>>
>>>>> Although seeing some peoples source code they are doing all sorts of
>>>>> stuff which I would of expected to be inside the orthoM method (like
>>>>> calling tan functions and dividing etc). So how exactly are you
>>>>> supposed to use this function?
>>>>>
>>>>> Steve
>>>>>
>>>>
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