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 >>>> >>> -- 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
