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 >>> >> -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
