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--- billboard [2020/01/10 12:22] – [Example: Grass Billboard] admin
+++ billboard [Unknown date] (current) – removed - external edit (Unknown date) 127.0.0.1
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-====== Billboard ======
-A billboard controls proxy instances of a basis mesh (source object).
-The billboard component is a mesh itself, into which proxies are merged. Much faster rendering is possible if proxy meshes are merge into one mesh, instead of rendering each mesh.
-We typically use this technique for grass or trees.
-It is not suitable for animated meshes.
-===== Example: Grass Billboard =====
-In this example we will display grass on multiplied planes inside of the billboard component.
-After applying the TGorillaGrassMaterial we are able to render different textures onto those planes and to manipulate vertices.
-The result should be a varying grass landscape with waving grass.
-<file pascal Form1.pas>
-procedure TForm1.FormCreate(Sender: TObject);
-var LBillboard : TPlane;
-    LPoolE : TGorillaBitmapPoolEntry;
-    LGrassMat : TGorillaGrassMaterialSource;
-    LAlg : TGorillaBillboardRectFilling;
-begin
-  // creating the source object - here a plane
-  LBillboard := TPlane.Create(fGorilla);
-  LBillboard.Scale.Point := Point3D(4, 4, 4);
-  // creating the grass material source
-  FGrassMat := TGorillaGrassMaterialSource.Create(FGorilla);
-  FGrassMat.Parent := FGorilla;
-  // now we load a pool of grass textures, the material shader
-  // randomly chooses from
-  with FGrassMat do
-  begin
-    LPoolE := Bitmaps.Add() as TGorillaBitmapPoolEntry;
-    LPoolE.DisplayName := 'Grass1';
-    LPoolE.Bitmap.LoadFromFile('grass1.png');
-    LPoolE := Bitmaps.Add() as TGorillaBitmapPoolEntry;
-    LPoolE.DisplayName := 'Grass2';
-    LPoolE.Bitmap.LoadFromFile('grass2.png');
-    LPoolE := Bitmaps.Add() as TGorillaBitmapPoolEntry;
-    LPoolE.DisplayName := 'Grass3';
-    LPoolE.Bitmap.LoadFromFile('grass3.png');
-    LPoolE := Bitmaps.Add() as TGorillaBitmapPoolEntry;
-    LPoolE.DisplayName := 'Grass4';
-    LPoolE.Bitmap.LoadFromFile('grass4.png');
-  end;
-  // creating the billboard control
-  FGrass := TGorillaBillboard.Create(FGorilla);
-  FGrass .Parent := FGorilla;
-  FGrass.AddSourceObject(LBillboard);
-  FGrass.MaterialSource := LGrassMat;
-  FGrass.SetSize(GORILLA_BILLBOARD_SIZE, GORILLA_BILLBOARD_SIZE, GORILLA_BILLBOARD_SIZE);
-  // create an individual filling algorithm to multiply the grass planes
-  // on elder Gorilla3D version TGorillaBillboardRectFilling
-  LAlg := TGorillaBillboardFlatFilling.Create(FGrass);
-  try
-    LAlg.Count := 1000;
-    FGrass.Fill(LAlg, true);
-  finally
-    FreeAndNil(LAlg);
-  end;
-</file>
-==== Interact with grass shader ====
-The default grass shader provides functionality to bend the grass planes at a certain point.
-To enable interaction, f.e. at mouse position, we can simply configure the TGorillaGrassMaterialSource:
-<file pascal Form1.pas>
-  FGrassMat.SpotRadius := 0.5;
-  FGrassMat.SpotEnabled := true;
-</file>
-And in the OnMouseMove event we can set the current interaction point like this:
-<file pascal Form1.pas>
-procedure TForm1.DoOnViewportMouseMove(ASender : TObject; AShiftState : TShiftState;
-  X, Y : Single);
-var LPt3D : TPoint3D;
-    LRayPos, LRayDir : TVector3D;
-begin
-  if FMove then
-  begin
-    if (ssLeft in AShiftState) then
-    begin
-      FGorilla.BeginUpdate();
-      try
-        LPt3D := FGorilla.ScreenToWorld(PointF(X, Y));
-        FGorilla.Context.Pick(X, Y, TProjection.Camera, LRayPos, LRayDir);
-        FGrass.RayCastIntersect(LRayPos, LRayDir, LPt3D);
-        // apply scaled light position
-        FGrassMat.Spot := TPoint3D(LPt3D);
-      finally
-        FGorilla.EndUpdate();
-      end;
-    end;
-    FLatest := PointF(X, Y);
-  end;
-end;
-</file>
-===== Example: Terrain Grass Billboard =====
-Since v0.8.1+ we've implemented a lot of new backend features (bounding volume hierarchy for TMeshDef, multiple billboard source objects, TGorillaModel support), which allows to multiple meshes and place those onto a terrain surface.
-The following example will create 64 billboards, filled up with 64 copies of a grass template model. The billboards will be attached as childs to the terrain and rendered above.
-All billboards will be placed as grid above the complete terrain.
-__Notice:__ We could multiply the template model into a single billboard component, but the idea behind it, is to use the performance optimization of frustum culling.
-By frustum culling only the visible billboard chunks will be rendered, therefore we can reduce vertex rendering a lot.
-So at first we will load a grass template model. //Keep the mesh as simple as possible, because vertex count will increase fastly.//
-To place a grass model copy in correct y-position on the terrain, we need to know vertices of the terrain. The new feature of bounding volume hierarchy (BVH) computation for TMeshDef's helps here a lot. It is 1000 times faster, than iterating of all vertices to find the correct position.
-For template model multiplication we use the new TGorillaBillboardTerrainFilling class, which automatically reads y-position from BVH.
-<file pascal>
-const
-  MAP_SIZE = 900; // terrain size (quadratic)
-  MAP_HEIGHT = MAP_SIZE / 4;
-var FGrassTemps : Array[0..0] of TGorillaModel;
-procedure TForm1.CreateGrass(ATerrain : TGorillaTerrain; const AAssetsPath : String);
-const  GORILLA_BILLBOARD_SIZE = 1;
-      GORILLA_MODEL_GRASS_1 = 'lowpoly-grass-planes.obj';
-var LTexPath      : String;
-    LGrass        : TGorillaBillboard;
-    LFillAlg      : TGorillaBillboardTerrainFilling;
-    LChunks       : Integer;
-    LChunksPerRow : Integer;
-    i             : Integer;
-    LChunkSize    : TPoint3D;
-    LX, LZ        : Single;
-begin
-  if not Assigned(ATerrain) then
-    raise Exception.Create('terrain not available - grass will be as child of the terrain');
-  // load the grass templates
-  LTexPath := IncludeTrailingPathDelimiter(AAssetsPath + 'grass');
-  FGrassTemps[0] := TGorillaModel.LoadNewModelFromFile(FViewport, nil,
-    LTexPath + GORILLA_MODEL_GRASS_1, []);
-  FGrassTemps[0].Visible := false; // it do not need to be shown
-  // create a list for all 64 billboard chunks
-  FGrassBillboards := TList<TGorillaBillboard>.Create();
-  // acquire a bounding volume hierarchy for much faster raytracing
-  // after usage, it will be destroyed, because it consumes a lot memory
-  // and we only need it for the moment
-  TMeshDef(ATerrain.Def).AcquireBVH();
-  try
-    LChunks := 64;
-    LChunksPerRow := Ceil(Sqrt(LChunks));
-    LChunkSize.X := (MAP_SIZE / LChunksPerRow);
-    LChunkSize.Y := MAP_HEIGHT;
-    LChunkSize.Z := (MAP_SIZE / LChunksPerRow);
-    for i := 0 to LChunks - 1 do
-    begin
-      // create multiple grass billboards to use frustum culling
-      LGrass := TGorillaBillboard.Create(FViewport);
-      LGrass.Parent := FViewport;
-      LGrass.Opaque := false; // allow translucent rendering
-      LGrass.TwoSide := true;
-      LGrass.Name := 'Grass' + IntToStr(i + 1);
-      // add the grass model as source object
-      // multiple source objects are possible and will be chosen randomly
-      LGrass.AddSourceObject(FGrassTemps[0]);
-      // set the size of billboard chunk
-      LGrass.SetSize(LChunkSize.X, LChunkSize.Y, LChunkSize.Z);
-      LX := -(MAP_SIZE / 2) + ((i mod LChunksPerRow) * LChunkSize.X);
-      LZ := (MAP_SIZE / 2) - (Floor(i / LChunksPerRow) * LChunkSize.Z);
-      // place billboard chunk over terrain
-      LGrass.Position.Point := Point3D(LX, 0, LZ);
-      LGrass.MaterialSource := FGrassTemps[0].Meshes[0].MaterialSource;
-      FGrassBillboards.Add(LGrass);
-      // fill up billboard chunk with 64 copies of our grass template
-      LFillAlg := TGorillaBillboardTerrainFilling.Create(LGrass, ATerrain);
-      try
-        LFillAlg.Count := 64;
-        LGrass.Fill(LFillAlg, true);
-      finally
-        FreeAndNil(LFillAlg);
-      end;
-      // we put grass billboard into terrain model
-      LGrass.Parent := ATerrain;
-    end;
-  finally
-    // at the end we destroy the bounding volume hierarchy again to free memory
-    TMeshDef(ATerrain.Def).ReleaseBVH();
-  end;
-end;
-</file>
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