// Given a sprite model, generate the internal VBO mesh
private __SpriteModel GenerateMesh(Sprite SpriteObj)
{
// A square mesh should always be defined in this way:
// ^ 2 ___ 3 Triangle 1: 0, 2, 1 (turns into the screen)
// | |\ | Triangle 2: 2, 3, 1
// y+ 0|_\|1
// x+ ----->
__SpriteModel Model = new __SpriteModel();
// 0. Get default color
Model.UniformColor = SpriteObj.GetColor();
// 1. Apply size (so we can scale first)
Model.Vertices[0] = new Vector2(0, 0);
Model.Vertices[1] = new Vector2(SpriteObj.GetGeometrySize().x, 0);
Model.Vertices[2] = new Vector2(0, SpriteObj.GetGeometrySize().y);
Model.Vertices[3] = new Vector2(SpriteObj.GetGeometrySize().x, SpriteObj.GetGeometrySize().y);
// 2. Rotate
float Theta = SpriteObj.GetRotation();
for(int i = 0; i < 4; i++)
{
Vector2 Point = new Vector2(Model.Vertices[i].x, Model.Vertices[i].y);
Point -= SpriteObj.GetRotationCenter();
Model.Vertices[i].x = Point.x * Mathf.Cos(Theta) - Point.y * Mathf.Sin(Theta);
Model.Vertices[i].y = Point.y * Mathf.Cos(Theta) + Point.x * Mathf.Sin(Theta);
}
// 3. Translate to position
for(int i = 0; i < 4; i++)
Model.Vertices[i] += new Vector3(SpriteObj.GetPosition().x, SpriteObj.GetPosition().y, SpriteObj.GetDepth());
// 4. Copy over the UV values
// Normalize the frame and offset values
Vector2 TextureSize = SpriteObj.GetTextureSize();
Vector2 NormalizedFrame = new Vector2(SpriteObj.GetSpriteSize().x / TextureSize.x, SpriteObj.GetSpriteSize().y / TextureSize.y);
Vector2 NormalizedPos = new Vector2(SpriteObj.GetSpritePos().x / TextureSize.x, SpriteObj.GetSpritePos().y / TextureSize.y);
// ***We need to take image coordinaes (top-left origin) and transform them to bottom-left origin
// UV origin is from the bottom-left
NormalizedPos.y = 1 - NormalizedPos.y;
NormalizedPos.y -= NormalizedFrame.y;
// Compute final UVs
Model.UVs[0] = new Vector2(NormalizedPos.x, NormalizedPos.y);
Model.UVs[1] = new Vector2(NormalizedPos.x + NormalizedFrame.x, NormalizedPos.y);
Model.UVs[2] = new Vector2(NormalizedPos.x, NormalizedPos.y + NormalizedFrame.y);
Model.UVs[3] = new Vector2(NormalizedPos.x + NormalizedFrame.x, NormalizedPos.y + NormalizedFrame.y);
// If the texture is flipped, just swap 0 <-> 1 and 2 <-> 3
if(SpriteObj.GetFlipped())
{
Vector2 temp = Model.UVs[0];
Model.UVs[0] = Model.UVs[1];
Model.UVs[1] = temp;
temp = Model.UVs[2];
Model.UVs[2] = Model.UVs[3];
Model.UVs[3] = temp;
}
// Done!
return Model;
}
