func (d *DrawImage) rebuildModel(display *Display) {
if len(d.vertex) != 2 {
d.vertex = make([][]float32, 2)
d.uv = make([][]float32, 2)
}
modelM := glm.NewIdentityMatrix4()
d.mvp = display.vp.Mul(modelM)
d.vertex[0] = scale(10, []float32{
-1, -1, 0,
-1, 1, 0,
1, 1, 0,
})
d.uv[0] = []float32{
1, 0.5,
1, 0.5,
1, 0.5,
}
d.vertex[1] = scale(10, []float32{
1, 1, 0,
1, -1, 0,
-1, -1, 0,
})
d.uv[1] = []float32{
1, 0.5,
1, 0.5,
1, 0.5,
}
}
func prepareModelViewProjection(width, height float32) *glm.Matrix4 {
modelM := glm.NewIdentityMatrix4()
// this is just 2d, so ignore the camera matrix
// camera at 0,0,1 (could be anything > 0 )
// looking at 0,0,0
// with the +Y is the Up vector
//
// could be replaced by a Identity matrix, but keeping this here
// since it make easier to turn the world upside down
viewM := glm.NewLookAtMatrix4(
glm.Vector3{0, 0, 1},
glm.Vector3{0, 0, 0},
glm.Vector3{0, -1, 0})
// in order to keep things simple,
// the 2d projection uses the center of screen as the point 0,0
// ie, the (top,left) == (-width/2, heiht/2)
projection := glm.NewOrthoMatrix4(-width/2, width/2, -height/2, height/2, 0, 100)
return projection.Mul(viewM).Mul(modelM)
}