rhetoric

im really stuck with some basics, and therefore i need your help.

what i want is a plane (from jit.gl.gridshape) fitting exactly into my window. (there is going to be a texture, later)

e.g. my window is 320x240. the plane is scaled to 1x0.75 (i dont mention the z-scale). so it has the same aspect ratio.

the camera has a lensangle of 45 degrees (default) and i tweek the position (only on z-axis) to make the plane fit exactly into the window. by just scrubing i get the result of about 1.82..

but i want to get this result by calculating it. it want it precise. but how???????

shouldnt it be a simple calculation with a isosceles triangle, where i need the height? (i've got a and alpha). or is there another trick i dont know. it must be simple, must'nt it?

what i want is a plane (from jit.gl.gridshape) fitting exactly into my window. (there is going to be a texture, later)
e.g. my window is 320x240. the plane is scaled to 1x0.75 (i dont mention the z-scale). so it has the same aspect ratio.
the camera has a lensangle of 45 degrees (default) and i tweek the position (only on z-axis) to make the plane fit exactly into the window. by just scrubing i get the result of about 1.82.. 

but i want to get this result by calculating it. it want it precise. but how???????
shouldnt it be a simple calculation with a isosceles triangle, where i need the height? (i've got a and alpha). or is there another trick i dont know. it must be simple, must'nt it?

please see the attached patch..
thanks alot to everyone
rhe


im-stuck-plane-gridshape-fitting-exactly-into-my-jit-pwindow

Wondering where you got the triangle idea, am curious...

Don't really have an answer to that one but here's the patch again with a few other comments.

@transform_reset 2 on your gridshape (also @scale 1 1 1)

robtherich wrote on Sat, 16 May 2009 18:55

billboarding. thats the clue, thanks a lot for the hint. perfect.

@ seejayjames, the idea with the triangle is simple: if you imagine an isosceles triangle, the bottom would represent the plane and the upper corner the cameras position (imagine the scenario from above). i need to know the cameras positon.. since i know the lens_angle (aka the angle from the upper corner) and the plane's size aka the bottom, i could calclulate the height from the triangle, aka the shortest distance from the plane to the camera position..

i need to look up the formula, i guess its something with tangens(alpha).. but i didnt get a correct result with that approach, maybee i forgot a point..

robtherich wrote on Sat, 16 May 2009 18:55@transform_reset 2 on your gridshape (also @scale 1 1 1)

@ seejayjames, the idea with the triangle is simple: if you imagine an isosceles triangle, the bottom would represent the plane and the upper corner the cameras position (imagine the scenario from above). i need to know the cameras positon.. since i know the lens_angle (aka the angle from the upper corner) and the plane's size aka the bottom, i could calclulate the height from the triangle, aka the shortest distance from the plane to the camera position..
i need to look up the formula, i guess its something with tangens(alpha).. but i didnt get a correct result with that approach, maybee i forgot a point..

i'm stuck: plane (gridshape) fitting exactly into my jit.pwindow.