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texture - texture
face - face of cube to select. This should be one of the following values: 0: left (negative X) face 1: forward (positive Z) face - this is the default. 2: right (positive X) face 3: backward (negative Z) face 4: up (positive Y) face 5: down (negative Y) face |
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Selects a cube face for direct rendering to a texture.
This command should only be used when you wish to draw directly to a cubemap texture in real-time. Otherwise, just loading a pre-rendered cubemap with a flag of 128 will suffice. To understand how this command works exactly it is important to recognise that Blitz treats cubemap textures slightly differently to how it treats other textures. Here's how it works... A cubemap texture in Blitz actually consists of six images, each of which must be square 'power' of two size - e.g. 32, 64, 128 etc. Each corresponds to a particular cube face. These images are stored internally by Blitz, and the texture handle that is returned by LoadTexture/CreateTexture when specifying the cubemap flag, only provides access to one of these six images at once (by default the first one, or '0' face). This is why, when loading a cubemap texture into Blitz using LoadTexture, all the six cubemap images must be laid out in a specific order (0-5, as described above), in a horizontal strip. Then Blitz takes this texture and internally converts it into six separate images. So seeing as the texture handle returned by CreateTexture / LoadTexture only provides access to one of these images at once (no. 1 by default), how do we get access to the other five images? This is where SetCubeFace comes in. It will tell Blitz that whenever you next draw to a cubemap texture, to draw to the particular image representing the face you have specified with the face parameter. Now you have the ability to draw to a cubemap in real-time. To give you some idea of how this works in code, here's a function that updates a cubemap in real-time. It works by rendering six different views and copying them to the cubemap texture buffer, using SetCubeFace to specify which particular cubemap image should be drawn to. ; Start of code Function UpdateCubeMap( tex,camera ) tex_sz=TextureWidth(tex) ; do left view SetCubeFace tex,0 RotateEntity camera,0,90,0 RenderWorld ; copy contents of backbuffer to cubemap CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do forward view SetCubeFace tex,1 RotateEntity camera,0,0,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do right view SetCubeFace tex,2 RotateEntity camera,0,-90,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do backward view SetCubeFace tex,3 RotateEntity camera,0,180,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do up view SetCubeFace tex,4 RotateEntity camera,-90,0,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do down view SetCubeFace tex,5 RotateEntity camera,90,0,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) EndFunction ; End of code All rendering to a texture buffer affects the currently selected face. Do not change the selected cube face while a buffer is locked. Finally, you may wish to combine the vram 256 flag with the cubic mapping flag when drawing to cubemap textures for faster access. See also: CreateTexture, LoadTexture, SetCubeMode. |
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; SetCubeFace Example
; ------------------- width=640 height=480 depth=0 mode=0 Graphics3D width,height,depth,mode SetBuffer BackBuffer() ; If user's graphics card does not support cubic mapping then quit example If GfxDriverCaps3D()<110 Then RuntimeError "Sorry, your graphics card does not support cubic environemnt maps." cam=CreateCamera() PositionEntity cam,0,10,-10 ; Create separate camera for updating cube map - this allows us to manipulate main camera and cube camera which avoids any confusion cube_cam=CreateCamera() HideEntity cube_cam light=CreateLight() RotateEntity light,90,0,0 ; Load object we will apply cubemap to - the classic teapot teapot=LoadMesh("media/teapot.x") ScaleEntity teapot,3,3,3 PositionEntity teapot,0,10,0 ; Create some scenery ; ground ground=CreatePlane() EntityColor ground,168,133,55 ground_tex=LoadTexture("media/sand.bmp") ScaleTexture ground_tex,10,10 EntityTexture ground,ground_tex ; sky sky=CreateSphere(24) ScaleEntity sky,500,500,500 FlipMesh sky EntityFX sky,1 sky_tex=LoadTexture("media/sky.bmp") EntityTexture sky,sky_tex ; cactus cactus=LoadMesh("media/cactus2.x") FitMesh cactus,-5,0,-5,2,6,.5 ; camel camel=LoadMesh("media/camel.x") FitMesh camel,5,0,-5,6,5,4 ; Load ufo to give us a dynamic moving object that the cubemap will be able to reflect ufo_piv=CreatePivot() PositionEntity ufo_piv,0,15,0 ufo=LoadMesh("media/green_ufo.x",ufo_piv) PositionEntity ufo,0,0,10 ; Create texture with color + cubic environment map + store in vram flags tex=CreateTexture(256,256,1+128+256) ; Apply cubic environment map to teapot EntityTexture teapot,tex While Not KeyDown(1) ; Control camera ; mouse look mxs#=mxs#+(MouseXSpeed()/5.0) mys#=mys#+(MouseYSpeed()/5.0) RotateEntity cam,mys#,-mxs#,0 MoveMouse width/2,height/2 ; move camera forwards/backwards/left/right with cursor keys If KeyDown(200)=True Then MoveEntity cam,0,0,.2 ; move camera forward If KeyDown(208)=True Then MoveEntity cam,0,0,-.2 ; move camera back If KeyDown(205)=True Then MoveEntity cam,.2,0,0 ; move camera left If KeyDown(203)=True Then MoveEntity cam,-.2,0,0 ; move camera right ; Turn ufo pivot, causing child ufo mesh to spin around it (and teapot) TurnEntity ufo_piv,0,2,0 ; Hide our main camera before updating cube map - we don't need it to be rendererd every time cube_cam is rendered HideEntity cam ; Update cubemap UpdateCubemap(tex,cube_cam,teapot) ; Show main camera again ShowEntity cam RenderWorld Text 0,0,"Use mouse to look around" Text 0,20,"Use cursor keys to change camera position" Flip Wend Function UpdateCubemap(tex,camera,entity) tex_sz=TextureWidth(tex) ; Show the camera we have specifically created for updating the cubemap ShowEntity camera ; Hide entity that will have cubemap applied to it. This is so we can get cubemap from its position, without it blocking the view HideEntity entity ; Position camera where the entity is - this is where we will be rendering views from for cubemap PositionEntity camera,EntityX#(entity),EntityY#(entity),EntityZ#(entity) CameraClsMode camera,False,True ; Set the camera's viewport so it is the same size as our texture - so we can fit entire screen contents into texture CameraViewport camera,0,0,tex_sz,tex_sz ; Update cubemap ; do left view SetCubeFace tex,0 RotateEntity camera,0,90,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do forward view SetCubeFace tex,1 RotateEntity camera,0,0,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do right view SetCubeFace tex,2 RotateEntity camera,0,-90,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do backward view SetCubeFace tex,3 RotateEntity camera,0,180,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do up view SetCubeFace tex,4 RotateEntity camera,-90,0,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; do down view SetCubeFace tex,5 RotateEntity camera,90,0,0 RenderWorld CopyRect 0,0,tex_sz,tex_sz,0,0,BackBuffer(),TextureBuffer(tex) ; Show entity again ShowEntity entity ; Hide the cubemap camera HideEntity camera End Function |