Drawing triangles quickly
Blitz3D Forums/Blitz3D Programming/Drawing triangles quickly
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| I need to draw many triangle shapes on a texture quickly(either red or blue). can someone suggest the quickest way to do that? |
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| All the same size? Or different sizes? Are they supposed to be solid, or alphaed (see through)? |
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| different size and alphaed. if you know how to color a selected triangle on a textured mesh/surface, in an alphaed color it would be better. EDIT: it not must be alphaed, i can use multiple layers. |
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| Well, you can use VertexColor() to alter each individual vertex. I'm afraid i can't think of any quick way of doing what you need though... |
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| and slow way? quick= not more then ~15 sec for a 2048*2048 bitmap |
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| Slow would be writepixelfast and readpixel fast. What i'd do is create a triangle mesh. Entitycolor it the colour i need, and scale it the scale i need. Then, renderworld, readpixel on the triangle and copy the whole thing onto the texture. Obviously missing any black pixels, and manually writeing the alpha info at the same time. I'd say about 0.3 secs per triangle tops. Depends on the size of course. Very large triangles will take alot more time. |
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| Well, I think I will need here an external .net program using gdi+. does blitz supports gdi+? |
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| I don't think so. Can you explain more about what your trying to do? |
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| I'm having a b3d textured(2048*2048) model loaded to blitz(done). Now i have the camera movin there using keys and mouse(done). now i also want that when user press a specified key all the visible polygons to the camera on the model(done) would be coloured blue and the rest would be red(not done). The loaded model may vary. |
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| In which case use vertexcolor .... you can also use the optional alpha parameter if you set entityfx to 2+32. First unweld the mesh if you haven't already done so to ensure you can colour each individual triangle it's own color. I have a function which does this if you need it. Next use a function which calculates the triangle normal rather than the averaged shared vertex normal ( as per updatenormals ) function .. Function MESHnormals( mesh ) For su = 1 To CountSurfaces(mesh ) s = GetSurface( mesh , su ) For t = 0 To CountTriangles( s )-1 v0 = TriangleVertex( s, t, 0 ) v1 = TriangleVertex( s, t, 1 ) v2 = TriangleVertex( s, t, 2 ) ax# = VertexX( s, v1 ) - VertexX( s, v0 ) ay# = VertexY( s, v1 ) - VertexY( s, v0 ) az# = VertexZ( s, v1 ) - VertexZ( s, v0 ) bx# = VertexX( s, v2 ) - VertexX( s, v1 ) by# = VertexY( s, v2 ) - VertexY( s, v1 ) bz# = VertexZ( s, v2 ) - VertexZ( s, v1 ) Nx# = ( ay * bz ) - ( az * by ) Ny# = ( az * bx ) - ( ax * bz ) Nz# = ( ax * by ) - ( ay * bx ) Ns# = Sqr( Nx * Nx + Ny*Ny + Nz*Nz ) Nx = Nx / Ns Ny = Ny / Ns Nz = Nz / Ns For v = v0 To v2 VertexNormal s, v, Nx, Ny, Nz Next Next Next End Function Then use a function like so ... by passing both the mesh and the camera entities. Function TRIScolor( Mesh , Camera ) ;set mesh to vertexcolor EntityFX Mesh, 2 ;get cameras direction normal TFormNormal 0,0,1,Camera, 0 CamNx# = TFormedX() CamNy# = TFormedY() CamNz# = TFormedZ() For su = 1 To CountSurfaces( Mesh ) s = GetSurface( Mesh , su ) For t = 0 To CountTriangles( s ) - 1 ;get first vertex in triangle - normals should be same on each v0 = TriangleVertex( s, t, 0 ) TriNX# = VertexNX( s, v0 ) TriNy# = VertexNY( s, v0 ) TriNz# = VertexNZ( s, v0 ) ;compute dot product of camera normal and tri normal CdotN# = CamNx*TriNx + CamNY * TriNy + CamNz * TriNz If CdotN < 0 Then ;triangle facing camera - color red For v = v0 To v0 + 2 VertexColor s, v, 255,0,0 Next Else ;triangle not facing camera - color white For v = v0 To v0 + 2 VertexColor s, v, 255,255,255 Next EndIf Next Next End Function Stevie |
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| thank you very much. somewhy the algorithm for finding the facing triangles is not fine, because... it just wrong, it colours me some wrong triangles and some wont be coloured. When using the function I refer to the camera pivot and not the camera itselfs as its parent is the pivot. EDIT: Wait checking again.... don't respond EDIT: Checked and yes it not workin right In every place im placing the camera it shows the same. just rotating the camera change the colors |
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| Oops, sorry just typed that in without proper testing .. forgot to transform the vertex normal into worldspace coords. This works .. Function TRIScolor( Mesh , Camera ) ;set mesh to vertexcolor EntityFX Mesh, 2+4 ;get cameras direction normal TFormNormal 0,0,1,Camera, 0 CamNx# = TFormedX() CamNy# = TFormedY() CamNz# = TFormedZ() For su = 1 To CountSurfaces( Mesh ) s = GetSurface( Mesh , su ) For t = 0 To CountTriangles( s ) - 1 ;get first vertex in triangle - normals should be same on each v0 = TriangleVertex( s, t, 0 ) TFormVector VertexNX( s, v0 ), VertexNY( s, v0 ) , VertexNZ( s, v0 ) , Mesh , 0 TriNx# = TFormedX() TriNy# = TFormedY() TriNz# = TFormedZ() ;compute dot product of camera normal and tri normal CdotN# = CamNx*TriNx + CamNY * TriNy + CamNz * TriNz If CdotN <= .001 Then ;triangle facing camera - color red For v = v0 To v0 + 2 VertexColor s, v, 255,0,0 Next Else ;triangle not facing camera - color white For v = v0 To v0 + 2 VertexColor s, v, 255,255,255 Next EndIf Next Next End Function |
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| Not working yet. only the rotation of the camera change the colors. I need that when i am on a specified place it would color different the model than on another position. EDIT: I thought about it and I may didn't explained myself well. i need to detect if i pass a line from the triangle to the camera, would be there any other triangles in the way. |
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| If there are other triangles in the way then the triangle is probably hidden from view so you wouldn't be able to see the colour? Sorry but you're still not making perfect sense? Tell us what the purpose of this function would be in game. |
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| Ok sorry. I have 2 cameras. one above the model(top view) and one is the character. when running this function, a line would be passed to every single triangle and would check whether there are triangles in the way or not. if there aren't, the camera can see the triangle and it would be colored red. if there are some in the way, the camera cant see it, and the triangle would colored blue or white and some of them might be visible for the camera of the top view. EDIT: It just like EntityVisible, but for Entity-Triangle instead of Entity-Entity mode. |
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| Well that's a fair bit different from what you originally posted!! Ok, I can't think of a faster solution atm. This will likely be slow due to the number of linepicks required. ...... * Make the level geometry pickable : entitypickmode 2. * Set each mesh to vertexcolor : EntityFX Mesh, 2 * In the function below, the 'Viewer' is whatever entity you want the triangles to be coloured in relation to. It can be a camera, entity, pivot etc.. If it still doesn't work for you then you will need to either send or post me some code. Stevie |
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| "now i also want that when user press a specified key all the visible polygons to the camera on the model..." but nvm. Thank you very much for your help, most of the triangles are colored correct, some aren't maybe if ill change the model it would be better. |
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| Your welcome. Try playing about with the .000001 threshold for determining whether a poly is facing the camera. Alternatively, post your code. |
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| This is probably several days late and dollars short, but: Why not put a bright blue spotlight at the camera position? Depending on your needs this might suit and would be fast and easy, although: - It would also light up other objects (but not the player's ship itself if you do it right) - It would not be a pure blue color, but would alter the base texture color according to distance and angle. If you can tolerate those factors, it might simplify things. |
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