Accessing/Modifying the Projection Matrix

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Mr Anderson

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Posted: 16th Mar 2004 06:34

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I learned how to make high res images... I just need to be able to change the projection matrix.

anyone?

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Mr Anderson

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Posted: 21st Mar 2004 03:22

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Ok maybe I sounded alien.

In OpenGL there is something called the projection matrix. I'm sure that DirectX has an equivilant mechanism, I just wanted to know if you could manipulate it within DBPro.

I wanted to create screen shots that are very high resolution. The only technique I have found manipulates the projection matrix part of the render pipeline. And you render out several square images that fit together to form the final image.

Anyone

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walaber

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Posted: 21st Mar 2004 03:52

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oooh... highly unlikely... DBPro doesn't let the user quite that deep into the DirectX pipeline.

I suppose you could try rendering the scene several times from different camera positions, and then re-assembling the screen later, but I think you would run into perspective problems...

tough one.

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Bulleyes

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Posted: 21st Mar 2004 11:09

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You can't, but you can sorta like altering the projection matrix by fiddling with the camera parameters like FOV, far/near clipping plane, etc. I don't know whether this will help you though.

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DrakeX

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Posted: 21st Mar 2004 16:35

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strangely, there is a way to retrieve the projection matrix, but no way to set it. in the 3dmath command set, there is the PROJECTION MATRIX4 command that fills a matrix with the current projection matrix, but.. i can't find a command that set the projection matrix!

OK, i was a bit conservative with my release date. predicted DBP P6 release date: Bjork 45, 3418

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AtomR

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Posted: 21st Mar 2004 20:14

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BUILD LOOKAT LHMATRIX4
BUILD LOOKAT RHMATRIX4
BUILD ORTHO LHMATRIX4
BUILD ORTHO RHMATRIX4
BUILD FOV LHMATRIX4
BUILD FOV RHMATRIX4
BUILD PERSPECTIVE LHMATRIX4
BUILD PERSPECTIVE RHMATRIX4
BUILD REFLECTION MATRIX4

Have you tried using these commands? I honestly don't know what they are for but maybe it's what you want.

I think that DBS should invest a little time making proper documentation for the 3d maths commands, if nothing else's. They are really not at all self explantory. On the other hand if words like projection matrix, perspective matrix, loot at matrix doesn't say anything it's highly likelly the documentation wouldn't help much either. Can anyone point me to some tutorial sites where I/we could learn a bit more about these technical terms?

Take care
AtomR

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DrakeX

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Posted: 22nd Mar 2004 05:16

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those commands let you make projection matrices, but there is no command to actually apply the matrix after you've made it.

OK, i was a bit conservative with my release date. predicted DBP P6 release date: Bjork 45, 3418

cookies, milk, and communism.

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Neophyte

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Posted: 22nd Mar 2004 08:07

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The 3d Math command set is mostly for shaders. If you want to apply your own projection matrix you'll have to write a shader to do it, and pass in the value of whatever projection matrix you want. This is a bit over kill but unfortuanately its the only way right now. Until Lee or Mike decided to allow us apply the matrixs to object and whatnot I'm afraid a shader is your only route.

@Mr Anderson

I'm not entirely sure what technique you found but I just don't understand how modifing the projection matrix would give higher resolution. If you want higher resolution screen shots just switch you resolution to something bigger and snap a picture. Problem solved.

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Dmitry K

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Posted: 23rd Mar 2004 10:19

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You must use Set Camera Fov, Set Camera Range

`*******************************************************************************
`*                            Free License Agreement.                          *
`*                                                                             *
`*   The user/developer agrees to include a visible credit to "Dmitry Kuschev" *
`*   within your programs documentation and or web site.                       *
`*                                                                             *
`*   The user/developer agrees to NOT offer the this source code for Sale.     *
`*                                                                             *
`*   Providing the user/Developer agrees in full to the previous Free          *
`*   License Agreement clauses, the user/developer may use this source         *
`*   code FREELY in all their products, commercial or otherwise.               *
`*                                                                             *
`*******************************************************************************

Dim Matrix4(16) As Float

Randomize Timer()

FOV#=RND(3600)/10.0
Near#=RND(1000)-RND(1000)
Far#=RND(5000)-RND(5000)

BuildProjectionMatrix(FOV#, (Screen Width()*1.0)/(Screen Height()*1.0), Near#, Far#)

Sync Rate 0
Sync On

Do
   Set Cursor 0, 0
   Print "Accessing/Modifying the Projection Matrix by Dmitry K"
   Print
   Print "FOV# = ", FOV#
   Print "Near# = ", Near#
   Print "Far# = ", Far#
   Print
   Print "GetFOVFromProjectionMatrix() = ", GetFOVFromProjectionMatrix()
   Print "GetNearFromProjectionMatrix() = ", GetNearFromProjectionMatrix()
   Print "GetFarFromProjectionMatrix() = ", GetFarFromProjectionMatrix()
   Print

SetViewPortProjectionMatrix(GetFOVFromProjectionMatrix(), GetNearFromProjectionMatrix(), GetFarFromProjectionMatrix())

Print "GetFOVFromViewPort() = ", GetFOVFromViewPort()
   Sync
Loop

Function SetViewPortProjectionMatrix(FOV#, Near#, Far#)
   Set Camera FOV FOV#
   Set Camera Range Near#, Far#
EndFunction

Function BuildProjectionMatrix(FOV#, AspectRatio#, Near#, Far#)
   BuildFOVLHMatrix4(FOV#, AspectRatio#, Near#, Far#)
EndFunction

Function BuildFOVLHMatrix4(FOV#, Aspect#, Near#, Far#)
   Height#=1.0/Tan(FOV#/2.0)
   Width#=Height#/Aspect#
   Matrix4(1)=Width#
   Matrix4(2)=0.0
   Matrix4(3)=0.0
   Matrix4(4)=0.0
   Matrix4(5)=0.0
   Matrix4(6)=Height#
   Matrix4(7)=0.0
   Matrix4(8)=0.0
   Matrix4(9)=0.0
   Matrix4(10)=0.0
   Matrix4(11)=Far#/(Far#-Near#)
   Matrix4(12)=1.0
   Matrix4(13)=0.0
   Matrix4(14)=0.0
   Matrix4(15)=-1.0*Near#*(Far#/(Far#-Near#))
   Matrix4(16)=0.0
EndFunction

Function GetFOVFromViewPort()
   r=Make Matrix4(100)
   Projection Matrix4 100
   GetFOVResult#=Atan(1.0/(X Vector2(100)*((Screen Width()*1.0)/(Screen Height()*1.0))))*2.0
   If GetFOVResult# <= 0.0 Then Inc GetFOVResult#, 360.0
EndFunction GetFOVResult#

Function GetFOVFromProjectionMatrix()
   GetFOVResult#=Atan(1.0/(Matrix4(1)*((Screen Width()*1.0)/(Screen Height()*1.0))))*2.0
   If GetFOVResult# <= 0.0 Then Inc GetFOVResult#, 360.0
EndFunction GetFOVResult#

Function GetNearFromProjectionMatrix()
   NearResult#=-1.0*Matrix4(15)/Matrix4(11)
EndFunction NearResult#

Function GetFarFromProjectionMatrix()
   Near#=-1.0*Matrix4(15)/Matrix4(11)
   FarResult#=Near#/(1.0-1.0/Matrix4(11))
EndFunction FarResult#

+ Code Snippet

`*******************************************************************************
`*                            Free License Agreement.                          *
`*                                                                             *
`*   The user/developer agrees to include a visible credit to "Dmitry Kuschev" *
`*   within your programs documentation and or web site.                       *
`*                                                                             *
`*   The user/developer agrees to NOT offer the this source code for Sale.     *
`*                                                                             *
`*   Providing the user/Developer agrees in full to the previous Free          *
`*   License Agreement clauses, the user/developer may use this source         *
`*   code FREELY in all their products, commercial or otherwise.               *
`*                                                                             *
`*******************************************************************************

Dim Matrix4(16) As Float

Randomize Timer()

FOV#=RND(3600)/10.0
Near#=RND(1000)-RND(1000)
Far#=RND(5000)-RND(5000)

BuildProjectionMatrix(FOV#, (Screen Width()*1.0)/(Screen Height()*1.0), Near#, Far#)

Sync Rate 0
Sync On

Do
   Set Cursor 0, 0
   Print "Accessing/Modifying the Projection Matrix by Dmitry K"
   Print
   Print "FOV# = ", FOV#
   Print "Near# = ", Near#
   Print "Far# = ", Far#
   Print
   Print "GetFOVFromProjectionMatrix() = ", GetFOVFromProjectionMatrix()
   Print "GetNearFromProjectionMatrix() = ", GetNearFromProjectionMatrix()
   Print "GetFarFromProjectionMatrix() = ", GetFarFromProjectionMatrix()
   Print

   SetViewPortProjectionMatrix(GetFOVFromProjectionMatrix(), GetNearFromProjectionMatrix(), GetFarFromProjectionMatrix())

   Print "GetFOVFromViewPort() = ", GetFOVFromViewPort()
   Sync
Loop

Function SetViewPortProjectionMatrix(FOV#, Near#, Far#)
   Set Camera FOV FOV#
   Set Camera Range Near#, Far#
EndFunction

Function BuildProjectionMatrix(FOV#, AspectRatio#, Near#, Far#)
   BuildFOVLHMatrix4(FOV#, AspectRatio#, Near#, Far#)
EndFunction

Function BuildFOVLHMatrix4(FOV#, Aspect#, Near#, Far#)
   Height#=1.0/Tan(FOV#/2.0)
   Width#=Height#/Aspect#
   Matrix4(1)=Width#
   Matrix4(2)=0.0
   Matrix4(3)=0.0
   Matrix4(4)=0.0
   Matrix4(5)=0.0
   Matrix4(6)=Height#
   Matrix4(7)=0.0
   Matrix4(8)=0.0
   Matrix4(9)=0.0
   Matrix4(10)=0.0
   Matrix4(11)=Far#/(Far#-Near#)
   Matrix4(12)=1.0
   Matrix4(13)=0.0
   Matrix4(14)=0.0
   Matrix4(15)=-1.0*Near#*(Far#/(Far#-Near#))
   Matrix4(16)=0.0
EndFunction

Function GetFOVFromViewPort()
   r=Make Matrix4(100)
   Projection Matrix4 100
   GetFOVResult#=Atan(1.0/(X Vector2(100)*((Screen Width()*1.0)/(Screen Height()*1.0))))*2.0
   If GetFOVResult# <= 0.0 Then Inc GetFOVResult#, 360.0
EndFunction GetFOVResult#

Function GetFOVFromProjectionMatrix()
   GetFOVResult#=Atan(1.0/(Matrix4(1)*((Screen Width()*1.0)/(Screen Height()*1.0))))*2.0
   If GetFOVResult# <= 0.0 Then Inc GetFOVResult#, 360.0
EndFunction GetFOVResult#

Function GetNearFromProjectionMatrix()
   NearResult#=-1.0*Matrix4(15)/Matrix4(11)
EndFunction NearResult#

Function GetFarFromProjectionMatrix()
   Near#=-1.0*Matrix4(15)/Matrix4(11)
   FarResult#=Near#/(1.0-1.0/Matrix4(11))
EndFunction FarResult#

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DarkBASIC Professional Discussion / Accessing/Modifying the Projection Matrix