One more pseudo-stencilShadow code ...

Blitz3D Forums/Blitz3D Programming/One more pseudo-stencilShadow code ...

Paolo (Posted 2005) [#1]

This is similar to the first demo we saw using stencil shadows, but this time it is completely done with Blitz functions and it only require two RenderWorld()'s. I would like to hear if someone get an idea... I think this might be useful for casting simple pre-made shadow volume onto geometry ... Read the comments, they are pretty simple: Graphics3D 640,480,32,1 AmbientLight 70,70,70 l=CreateLight(2) PositionEntity l,-5,5,5 LightRange l,15 cam=CreateCamera() CameraRange cam,.01,200 CameraClsColor cam,64,64,64 ;create some scene elements: c1=CreateCube() EntityFX c1,1 EntityColor c1,64,64,64 UpdateNormals c1 c3=CreateCylinder(16) EntityFX c3,1 EntityColor c3,255,255,255 PositionEntity c3,1.5,.5,1.5 UpdateNormals c3 pl=CreatePlane(16) PositionEntity pl,0,-2,0 ;-------------------------------- ;the next cube is a simulated shadow-volume c2=CreateCube() ScaleMesh c2,1,1,5 RotateEntity c2,-30,40,0 PositionEntity c2,1,0,1 EntityFX c2,1+16:EntityBlend c2,2 EntityColor c2,128,128,128 ;---------------------------------------------------- img=CreateImage(640,480) do_render=1 While Not KeyDown(1) TurnEntity c2,0,0,.3 ;->turn the shadow-volume TurnEntity c3,.1,.2,.3 If KeyDown(200) MoveEntity cam,0,0,.1 If KeyDown(208) MoveEntity cam,0,0,-.1 If KeyDown(203) MoveEntity cam,-.1,0,0 If KeyDown(205) MoveEntity cam,.1,0,0 TurnEntity cam,MouseYSpeed()/12.0,-MouseXSpeed()/12.0,0 RotateEntity cam,EntityPitch(cam),EntityYaw(cam),0 MoveMouse GraphicsWidth()/2,GraphicsHeight()/2 If KeyHit(57) show=Not show If KeyHit(28) do_render=Not do_render ;\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ If do_render=1 EntityFX c1,1:EntityColor c1,64,64,64 ;<-set up all scene elements with a single color (64,64,64) EntityFX c3,1:EntityColor c3,64,64,64 EntityFX pl,1:EntityColor pl,64,64,64 ShowEntity c2 ;<- show "shadow-volumes" RenderWorld ;capture the image two times to mask all ;the pixels except the pixels from the intersection: GrabImage img,0,0:MaskImage img,64,64,64 Color 16,16,16:Rect 0,0,640,480,1 DrawImage img,0,0 GrabImage img,0,0:MaskImage img,16,16,16 ;-------------------------------------------------------- EntityFX c1,0:EntityColor c1,255,0,0 ;<- restore elements to default colors EntityFX c3,0:EntityColor c3,0,0,255 EntityFX pl,0:EntityColor pl,0,255,0 If Not show HideEntity c2 ;<- hide shadow-volumes for the next RenderWorld EntityBlend c2,2 Else EntityBlend c2,1:EntityAlpha c2,.25 EndIf Else EntityFX c1,1:EntityColor c1,64,64,64 EntityFX c3,1:EntityColor c3,64,64,64 EntityFX pl,1:EntityColor pl,64,64,64 ShowEntity c2:EntityBlend c2,2 EndIf ;/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ UpdateWorld RenderWorld ;At last the image with the ;"intersection-pixels" is drawn in front: If do_render DrawImage img,0,0 EndIf ;------------------------------------------ Color 255,255,255 Text 10,10,"Use Arrows+Mouse to move" Text 10,25,"Press SPACE to hide/show the 'shadow-volume'" If do_render=1 Text 10,40,"Press ENTER to see how the effect is done" Else Text 10,300,"As you can see now, there are 3 colors on the scene:" Text 10,315,"1 for the background and all elements (64,64,64)," Text 10,330,"1 for the shadow-volumes (16,16,16)," Text 10,345,"and 1 for the intersection between the bodies (32,32,32)," Text 10,360,"then I GrabImage() the whole screen and mask" Text 10,375,"all the pixels except the the ones from the intersection." EndIf Flip Wend MoveMouse 400,300:End

jfk EO-11110 (Posted 2005) [#2]

This is great. I wonder if it's hard to create shadow volumes on the fly for any mesh, including animated ones. Maybe there is some kind of formula that takes the light-to-mesh relation pitch/yaw and roll and returns the required scaling factors for the meshes copy that will be the basement for the shadow volume? I really like this method since it's using only built in commands. EDIT: I think you need to scale (stretch) the meshes on the vertex level, so you can move the vertices contrary the lights direction. Begin with the vertex that is closest to the light, this one has to stay where it is. all other vertices should be moved away from the light, depending on their distance to the meshes center. However, this requires realtime mesh deformation and may be pretty slow.

John Blackledge (Posted 2005) [#3]

It has possibilities, but if you put a sphere where the light is (and stand under the sphere) you can see that there are shadows beginning generated that shouldn't be.(?)

Braincell (Posted 2005) [#4]

jfk, where have you been? This is pretty old. fredborg recently showed a demo on these forums, didnt you see it? Its still here somewhere. It is possible to make shadows for unanimated meshes because you need vertex positions and you cant get that for animated meshes.

John Blackledge (Posted 2005) [#5]

Lenn, where have _you_ been? Can you read the other shadow thread on the Showcase and (pretty please) let us know where you're up to.

big10p (Posted 2005) [#6]

All I see is this: ...which doesn't look right at all, to me. What is supposed to be casting that shadow?

puki (Posted 2005) [#7]

Well, there is no object shadow casting as such - still, it is an interesting idea. It just doesn't work in its current format. So, as the author says, simple shadow stuff. An interesting idea though.

jfk EO-11110 (Posted 2005) [#8]

Lenn - didn't realize this is the same method fredborg used in his demo. I know it, and I already realized that it has the same problem, the shadows will be visible on both sides, on the sunny side and on the shady side of the object. Tho I didn't realize it's the same method. The thing that I found fascinating is the fact that the intersection can be used as a 2D shadow thing.

Paolo (Posted 2005) [#9]

I have been trying to get something with this but I can not go any longer ... there is just too many problems to resolve ... ... anyway, I think I can live with no-shadow-stuff for me :) Paolo.

Braincell (Posted 2005) [#10]

jfk, this isnt the same method as real stencil shadows. This is just pseud-stencil like he says, he isnt using the stencil buffer and other DirectX stuff. This is just the same concept which in software would always be kinda slow. Btw, i replied in fredborg's thread and i intend to finish the free stencil shadow system. So eurythmia, you might end up having shadows after all... if i get it all to work like i want it to. Also, yes stencil shadows will always be visible "on both sides". This is just the nature of the shadow system and in many games it is completely ignored, such as Neverwinter Nights. In doom3 they just didnt make surfaces that you could see the other side of, or if they made some sort of culling method i cant imagine a simple way to do it with a limited (high level) blitz command set... This problem can easily be avoided with careful placement and scene design.

Paolo (Posted 2005) [#11]

Lenn, yep, I was trying to get something using blitz functions only ... so anyway ... I hope you get to a good point with that system :)

Red Ocktober (Posted 2005) [#12]

hey Paolo... a quick 3DRAD (hahaha, do you remember back that far:) ) question... you did some multiplayer stuff with it... do you remember any reason why it might not want to allow more than 2 people to link up via multiplayer? everytime i try to get 3 or more, the 3rd player winds up messing up the host... it all works fine over a LAN, but the net is the where the problem comes in... do you need ipx over the internet as if tcp is being used? sorry about this... thanks... --Mike

Paolo (Posted 2005) [#13]

hi Mike ! Honestly now I have forgotten most of how to program in 3DRad, I think you might be talking about Virtual Gotcha, I remember we used to test the game over the net with 3 players and it did was working at that time, although when the game was "released" John Robin told me there was big problems with more than 3 players... I don't know what can be the problem by these days :( ... it is also strange the game works good over a Lan but not over the net, I can only think about it might be something RAD-relative ... ...and I don't think we were using ipx, only TCP ... Cheers! Paolo.

Red Ocktober (Posted 2005) [#14]

thx Paolo... d3@1m RAD :) how's Tecno coming along... --Mike

Paolo (Posted 2005) [#15]

I'm quite happy about how the game is coming, although is some kind of disappointment the so-slow-process to accomplish something ... you know, if I would have known 3 years ago about the hardness of game development I think I would have never begun this project ... :) Anyway the game is coming very good, don't know exactly when I will finish it but I know for sure that I will finish ... now it has became a personal challenge :) I'm always keeping an eye on your posts, but mainly I come to the forum to read ... don't post too much ... I can't think much in English language ! By the way, are you still thinking about self publishing for the subsim? the other day I was having a look at Valusoft, it seems they offer a very good deal, and if your game does well over the net they also offer store-publishing ... don't know for sure but if they accept Tecno, I think I will be publishing through them when the time comes ... Later! Paolo.

jfk EO-11110 (Posted 2005) [#16]

Lenn - i meant an older coder archive entry by Fredborg: http://www.blitzbasic.com/codearcs/codearcs.php?code=1010 not his recent stencil shadow demo.