# Mat4::Ortho() example **URL:** \ **Category:** PowerVR Insider\ **Created:** [March 12, 2010, 4:53pm UTC](https://forums.imgtec.com/t/mat4-ortho-example/628 "2010-03-12T16:53:53Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![johnf](https://avatars.discourse-cdn.com/v4/letter/j/848f3c/32.png) [@johnf](https://forums.imgtec.com/u/johnf)\ **Post date:** [March 12, 2010, 4:53pm UTC](https://forums.imgtec.com/t/mat4-ortho-example/628/1 "2010-03-12T16:53:53Z")
Hello, I’m using the 3\_00\_00\_06 SDK from TI for OMAP3530.  I have a simple gles2 app with a shader which works fine using a projection matrix.  I can rotate my model 45 degrees and get expected results.  When I use a PVRT::Mat4::Ortho() I end up with an unsatisfying blank screen.  In other words, // this works: float aspect = screenWidth/screenHeight; bool bRotate = false; PVRT::Mat4::PerspectiveFovFloatDepthRH(PI/6.0, aspect, 1.0, PVRT::Mat4::OGL, bRotate); // this doesn’t work: float NEAR\_CLIP=10.0; float FAR\_CLIP=-10.0; PVRT::Mat4::Ortho(screenWidth/-2.0, screenHeight/2.0, screenWidth/2.0, screenHeight/-2.0, NEAR\_CLIP, FAR\_CLIP, PVRT::Mat4::OGL, bRotate); Is there an example app which uses an orthographic projection?  A grep in the SDK sources didn’t turn up anything. Another data point: when I just use a rotation matrix of .001 degrees around the Y axis, (no additional perspective or ortho matrix) I get a thin vertical block of pixels suggesting depth clipping is against me.  I assume this will go away once proper near/far planes are set. Thanks! ---
**Author:** ![michax-2](https://avatars.discourse-cdn.com/v4/letter/m/b38774/32.png) [@michax-2](https://forums.imgtec.com/u/michax-2)\ **Post date:** [August 27, 2010, 1:58am UTC](https://forums.imgtec.com/t/mat4-ortho-example/628/2 "2010-08-27T01:58:14Z")
Perspective has another “scale” factory. So if you have small triangle created with size around 1.0f it will be as 1px in screen in Ortho mode. Try to use -1, 1, 1, -1 for left, top, right, bottom, and you will get similar result to Perspective ( considering scale ). But if you want Ortho for creating HUD, you will need to scale up your objects. You asked also for exmaple, Ortho is used in Water Demo. ---
**Author:** ![johnf](https://avatars.discourse-cdn.com/v4/letter/j/848f3c/32.png) [@johnf](https://forums.imgtec.com/u/johnf)\ **Post date:** [September 10, 2010, 9:26pm UTC](https://forums.imgtec.com/t/mat4-ortho-example/628/3 "2010-09-10T21:26:36Z")
Hi michax.  Thanks for your reply. I was not able to find source for the water or sailboat demo in the SDK nor elsewhere, but I had another look at using PVRTMatrixOrthoRHF() and it seems to be doing what I need.  I started with the 02\_HelloTriangle example in the GLES2 training, passed the matrix generated by  PVRTMatrixOrthoRHF() to glUniformMatrix4fv() instead of the identity matrix and got expected results. ---
**Author:** ![GordonMaclachlan](https://avatars.discourse-cdn.com/v4/letter/g/c68b51/32.png) [@GordonMaclachlan](https://forums.imgtec.com/u/GordonMaclachlan)\ **Post date:** [September 17, 2010, 9:31am UTC](https://forums.imgtec.com/t/mat4-ortho-example/628/4 "2010-09-17T09:31:42Z")
Please post further if you encounter any difficulties. Incidentally, the Water demo should be here, in the SDK: SDKPackageDemosWater ---
**Author:** ![StuartNeilson](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.imgtec.com/stuartneilson/32/2_2.png) [@StuartNeilson](https://forums.imgtec.com/u/StuartNeilson)\ **Post date:** [October 12, 2010, 3:52am UTC](https://forums.imgtec.com/t/mat4-ortho-example/628/5 "2010-10-12T03:52:25Z")
Thanks you for your sharing ! It need for me to understand about ortho  I’m studying about it ![Wink]() #