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Dynamic Collision Detection https://delphigl.com/forum/viewtopic.php?f=19&t=3182	Seite 1 von 1

Autor:	Stucuk [ Mi Aug 18, 2004 23:09 ]
Betreff des Beitrags:	Dynamic Collision Detection
Im wondering if anyone knows any decent(free) resources on Dynamic collision detection(3d not 2d). I basicaly need to work out if the players box has hit a face of a entity.

Autor:	noeska [ Do Aug 19, 2004 09:22 ]
Betreff des Beitrags:
There are some threads on the topic here on the german language boards. Basicly you have to do some bounding sphere checking. For some better results you could do boundix box checking. Think of the camera as a sphere, then: You know the camera position also you can say the size of the camera. Also you know the positions of your objects in the world, and the sizes of them (calculate them in advance). Now you can check all bounding spheres with your camere sphere. Before starting collision detection be sure to understand frustum culling.

Autor:	Stucuk [ Do Aug 19, 2004 16:30 ]
Betreff des Beitrags:
The current system i made is basic Code: function TQuake3BSP.CheckCollisionEntitys2(Pos : TVector3f) : boolean; var i,x,y,z : integer; Min,Max : TVector3f; EntityObject : TEntityObject; begin Result := false; for i := 0 to numOfBSPCollisionEntitys-1 do if not CollisionEntitys[i].passable then begin if CollisionEntitys[i].EoId > -1 then begin EntityObject := EntityObjects.EntityObject[CollisionEntitys[i].EoId]; Max := AddVector(AddVector(Models[EntityObject.ModelId].Max,EntityObject.Position),EntityObject.ParentOffset); Min := AddVector(AddVector(Models[EntityObject.ModelId].Min,EntityObject.Position),EntityObject.ParentOffset); end else begin Max := CollisionEntitys[i].Max; Min := CollisionEntitys[i].Min; end; for x := trunc(Pos.X-Player_Box.X) to trunc(Pos.X+Player_Box.X) do If (x > Min.X) and (x < Max.X) then for z := trunc(Pos.Z-Player_Box.Z) to trunc(Pos.Z+Player_Box.Z) do If (z > Min.Z) and (z < Max.Z) then for y := trunc(Pos.Y-Player_Box.Y) to trunc(Pos.Y) do If (y > Min.Y) and (y < Max.Y) then begin Result := true; if CollisionEntitys[i].TouchEnabled then CollisionEntitys[i].Touch(CollisionEntitys[i],nil); // touching it exit; end; end; end; It works fine for cubes but even if i wanted a cube only world, it wouldn't work with entitys that are rotated. Frustrum culling to my knowlage is basicaly working out an area in 3d space that is around the camera, if a point of an object is inside the area it can b seen.

Autor:	noeska [ Do Aug 19, 2004 18:19 ]
Betreff des Beitrags:
getting speedy collison detecting requires you to check as little as possible. i use bounding boxes for my meshes inside a scene. so first i check against frustum so i only render the visible items also for these visible objects i do boundinx box checking if a collsions is determined i go some deeper and go face checking. so 1. check against frustum 2. do boundix box check 3. do face check But i see you use bsp so you should be able to skip step 1. and 2. As you alreade render a small part of the bsp. And can use that same part for collision checking. Also you seem to have collision checking code? What is it that you do not understand? I think it is best you ask your question at the quake to delphi project.

Autor:	Stucuk [ Fr Aug 20, 2004 00:25 ]
Betreff des Beitrags:
the collision detection for the actual level is perectly fine. But entitys are another matter. Entitys can move around the map, so u need a system thats dynamic, the code i posted is for entity collision only and is basic. It doesn't allow for the entity to rotate, say u have a train, it goes around a corner, it doesn't keep facing the same way, it rotates. with the current system the collision side would think of it as if it hadn't rotated, thus rotated entitys are imposible, and if the entity was a cylendar then it would act like a cube.

Autor:	noeska [ Fr Aug 20, 2004 13:33 ]
Betreff des Beitrags:
For a dynamic entity with bounding box you need te have: - its position in the world - its size - the rotation (not needed when using a boundingsphere for the entity) Also you need to know the camera position (i asume you use a bounding sphere for your camera). Now you can do some math: - First subtract the camara pos from the object pos - With the outcome of the previous step do the rotation calculation. - now you can check if the sphere and the cube collide using something like Code: sqrt(calcposition*calcposition) < entitysize + camsize Of course the above has to be split up in x y z That should be it. Next you can check on individual faces. It goes the same way as for the bounding box method, but the calcuation has to be done many times. I personaly don't care a lot about face checking i rather split up my meshes in more smaller meshes.

Autor:	Stucuk [ Fr Aug 20, 2004 16:21 ]
Betreff des Beitrags:
Zitat: - With the outcome of the previous step do the rotation calculation. - now you can check if the sphere and the cube collide using something like Code: sqrt(calcpositioncalcposition) < entitysize + camsize What do u mean by rotation calculation, from the code u posted it doesn't look like it factors in rotation.... Also with the "size" wouldn't that mean that the Bounding Box would have to have the exact same dimentions for its width, height, depth.......... Camera's box isn't a box as such eather: Code:* Player_Stand := SetVector(8, 45, 8); Player_Crouch := SetVector(8, 16, 8); Player_Box := Player_Stand;

Autor:

Stucuk [ Fr Aug 20, 2004 20:42 ]

Betreff des Beitrags:

Found a rather large bug with just taking the bounding box for collision detection (personaly i don't get how face collisions would work if the player is inside the actual object and not touching a face), i made a nice(ok it looks bad..... just like a Half-Life elevator), but since the system works by the max and min of the object, the player can't get inside the elevator (since it considers everythign between the max and min a sloid part of it). Apart from the fact its compleatly unusable, the "parent - child" thign works (one when the parent entity moves all its "children" are moved with it, i.e buttons and doors on elevators).

If the elevator could b split into several bounding boxes the system could easily b modifyed, but looking at how the thing is stored (array of faces, each "model" has the faceindex and the amount of faces) i don't think its an option.

Code:

 
type TBSPModel = record
  min              : TVector3f;       // The min position for the bounding box
  max              : TVector3f;       // The max position for the bounding box.
  faceIndex        : integer;         // The first face index in the model
  numOfFaces       : integer;         // The number of faces in the model
  brushIndex       : integer;         // The first brush index in the model
  numOfBrushes     : integer;         // The number brushes for the model
end;
 
type TBSPFace = record
  textureID : integer;                   // The index into the texture array
  effect    : integer;                   // The index for the effects (or -1 = n/a)
  FaceType  : integer;                   // 1=polygon, 2=patch, 3=mesh, 4=billboard
  startVertIndex : integer;              // The starting index into this face's first vertex
  numOfVerts     : integer;              // The number of vertices for this face
  meshVertIndex  : integer;              // The index into the first meshvertex
  numMeshVerts   : integer;              // The number of mesh vertices
  lightmapID     : integer;              // The texture index for the lightmap
  lMapCorner : array[0..1] of integer;   // The face's lightmap corner in the image
  lMapSize   : array[0..1] of integer;   // The size of the lightmap section
  lMapPos  : TVector3f;                  // The 3D origin of lightmap.
  lMapVecs : array[0..1] of TVector3f;   // The 3D space for s and t unit vectors.
  Normal  : TVector3f;                  // The face normal.
  Size : array[0..1] of integer;         // The bezier patch dimensions.
end;
 

Dateianhänge:

_0057.jpg [203.61 KiB]
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Autor:	noeska [ Sa Aug 21, 2004 13:37 ]
Betreff des Beitrags:
i did not provide the rotation calculations, only the calculation of the collision after the rotation calculation. Read http://www.delphigl.com/script/do_show. ... 1&action=2 on how to do it. But if you know how to do the bounding box collision detection you already know how to do the face or even vertice. - read out a vertice (x,y,z) and (maybe) add the objects world pos to it. - read out the camera - the rotation (you can get that from the entity) Now again - First subtract the camara pos from the object pos (now face vertice + object pos) - With the outcome of the previous step do the rotation calculation. - now you can check if the sphere and the cube collide and that should be it. For a much better face collision see: http://www.gametutorials.com/Tutorials/ ... GL_Pg3.htm

Autor:

Stucuk [ So Aug 22, 2004 12:47 ]

Betreff des Beitrags:

From my understanding of ur code i don't think it would work right with rotations. (see the pic below, black being a cube thats rotated and blue being my guess at the areas of collision detection). Tho it may help with the elevator problem.

EDIT: tryed implementing ur code (face checking), apart from being slow, it only worked when the player is crouched.......

Code:

 
Function CheckFaceCollision(Vertex : Array of TBSPVertex; Amount : Integer; Pos,Collision,Extents : TVector3f) : Boolean;
var
x : integer;
Size,Max,Min,CPos : TVector3f;
begin
 
Max := SetVector(-999999,-999999,-999999);
Min := SetVector(999999,999999,999999);
 
For x := 0 to Amount-1 do
if Vertex[x].Position.X > Max.X then
Max.X := Vertex[x].Position.X
else
if Vertex[x].Position.Y > Max.Y then
Max.Y := Vertex[x].Position.Y
else
if Vertex[x].Position.Z > Max.Z then
Max.Z := Vertex[x].Position.Z
else
if Vertex[x].Position.X < Min.X then
Min.X := Vertex[x].Position.X
else
if Vertex[x].Position.Y < Min.Y then
Min.Y := Vertex[x].Position.Y
else
if Vertex[x].Position.Z < Min.Z then
Min.Z := Vertex[x].Position.Z;
 
Size := SubtractVector(Max,Min);
 
CPos := SubtractVector(Collision,Pos);
 
if Min3f(SqrtVector(ScaleVector3f(CPos,CPos)),AddVector(Size,Extents)) then
Result := True
else
Result := False;
 
end;
 
Function EO_CheckFaceCollision(EOId : Integer) : Boolean;
var
FaceIndex,FaceCount,x,y : Integer;
EntityObject : TEntityObject;
Vertex : Array of TBSPVertex;
begin
 
EntityObject := EntityObjects.EntityObject[Eoid];
 
FaceIndex := Q3Level.Models[EntityObject.ModelId].faceIndex;
FaceCount := Q3Level.Models[EntityObject.ModelId].numOfFaces;
 
Result := False;
 
for x := 0 to FaceCount-1 do
with Q3Level.Faces[FaceIndex+x] do
begin
SetLength(Vertex,numOfVerts);
 
for y := 0 to numOfVerts-1 do
begin
Vertex[y] := Q3Level.Vertices[startVertIndex + y];
//Vertex[y].Position := AddVector(Vertex[y].Position);
end;
 
if CheckFaceCollision(Vertex,numofverts,AddVector(EntityObject.Position,EntityObject.ParentOffset),Camera.position,Player_Box) then
begin
Result := True;
Exit;
end;
 
 
end;
 
end;
 

Dateianhänge:

collision_rot.JPG [ 10.42 KiB | 7875-mal betrachtet ]

Autor:	noeska [ So Aug 22, 2004 18:30 ]
Betreff des Beitrags:
i did not say it was fast. But first check with bounding boxes only and if that delivers a collsion do the face check for that entity. i just noticed you recalculate a bounding box each time? That's bad. You really should precalculate them! Maybe you get a nice speed improvement. extents is your camera size? What is it set to? try experimenting with that. Also try leaving out y collsion checking for the time being.... also i dont see rotation? With that missing it will not work.

Autor:	Stucuk [ So Aug 22, 2004 23:59 ]
Betreff des Beitrags:
i never added rotation cos it wouldn't work(to my knowlage anyway) so there was no point coding it. The elevator is made of 5 cubes, thats 5x6 sides which is 40 faces. all the faces should have 4 points so working out the mix/max shouldn't take much time at all. The extents are as follows Code: Player_Stand := SetVector(8, 45, 8); Player_Crouch := SetVector(8, 16, 8); Player_Box := Player_Stand; Stand and crouch are the only things the player_box can be.

Autor:	Stucuk [ Mo Aug 23, 2004 17:21 ]
Betreff des Beitrags:
Btw i checked it again and when crouching there is no collision detected at all. Just lags the pc.

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