func TriangleIntersection(V1, V2, V3, O, D mgl.Vec3) (out float32, hit bool) {
const EPSILON = 0.000001
var e1, e2 mgl.Vec3 //Edge1, Edge2
var P, Q, T mgl.Vec3
var det, inv_det, u, v, t float32
//Find vectors for two edges sharing V1
e1 = V2.Sub(V1)
e2 = V3.Sub(V1)
//Begin calculating determinant - also used to calculate u parameter
P = D.Cross(e2)
//if determinant is near zero, ray lies in plane of triangle
det = e1.Dot(P)
//NOT CULLING
if det > -EPSILON && det < EPSILON {
return 0, false
}
inv_det = 1 / det
//calculate distance from V1 to ray origin
T = O.Sub(V1)
//Calculate u parameter and test bound
u = T.Dot(P) * inv_det
//The intersection lies outside of the triangle
if u < 0 || u > 1 {
return 0, false
}
//Prepare to test v parameter
Q = T.Cross(e1)
//Calculate V parameter and test bound
v = D.Dot(Q) * inv_det
//The intersection lies outside of the triangle
if v < 0 || u+v > 1 {
return 0, false
}
t = e2.Dot(Q) * inv_det
if t > EPSILON { //ray intersection
return t, true
}
// No hit, no win
return 0, false
}
func NewParticleSystem(w *gamestate.World, numParticles int, Origin mgl.Vec3, initialSpeed, MaxLifetime float32) *ParticleSystem {
vertices := make([]ParticleVertex, numParticles)
directions := make([]NonTransformBuffer, numParticles)
for i := range vertices {
dir := mgl.Vec3{rand.Float32()*2 - 1, rand.Float32()*2 - 1, rand.Float32()*2 - 1}
for dir.Len() > 1 {
dir = mgl.Vec3{rand.Float32()*2 - 1, rand.Float32()*2 - 1, rand.Float32()*2 - 1}
}
dir = dir.Mul(initialSpeed)
vertices[i] = ParticleVertex{
Pos1: Origin,
Pos2: Origin.Sub(dir),
Lifetime: rand.Float32() * MaxLifetime,
}
directions[i] = NonTransformBuffer{dir}
}
buffer1, buffer2, nonTransformBuffer := gl.GenBuffer(), gl.GenBuffer(), gl.GenBuffer()
nonTransformBuffer.Bind(gl.ARRAY_BUFFER)
gl.BufferData(gl.ARRAY_BUFFER, helpers.ByteSizeOfSlice(directions), directions, gl.STATIC_DRAW)
buffer1.Bind(gl.ARRAY_BUFFER)
gl.BufferData(gl.ARRAY_BUFFER, helpers.ByteSizeOfSlice(vertices), vertices, gl.STREAM_DRAW)
buffer2.Bind(gl.ARRAY_BUFFER)
gl.BufferData(gl.ARRAY_BUFFER, helpers.ByteSizeOfSlice(vertices), uintptr(0), gl.STREAM_DRAW)
shapeData := CreateShapeDataBuffer()
TransformProg := gl.CreateProgram()
shader := helpers.MakeShader(gl.VERTEX_SHADER, "ParticleTFF.vs")
TransformProg.AttachShader(shader)
TransformProg.TransformFeedbackVaryings([]string{"v_Pos1", "v_Pos2", "v_Lifetime"}, gl.INTERLEAVED_ATTRIBS)
TransformProg.Link()
shader.Delete()
TransformProg.Use()
TransformLoc := ProgramLocations{}
helpers.BindLocations("particle transform", TransformProg, &TransformLoc)
renderProgram := helpers.MakeProgram("Particle.vs", "Particle.fs")
renderProgram.Use()
RenderLoc := RenderProgramLocations{}
helpers.BindLocations("particle render", renderProgram, &RenderLoc)
vaoTff1 := gl.GenVertexArray()
vaoTff2 := gl.GenVertexArray()
vaoRender1 := gl.GenVertexArray()
vaoRender2 := gl.GenVertexArray()
ps := ParticleSystem{
TransformProg: TransformProg,
TransformLoc: TransformLoc,
RenderProg: renderProgram,
RenderLoc: RenderLoc,
VaoTff1: vaoTff1,
VaoTff2: vaoTff2,
VaoRender1: vaoRender1,
VaoRender2: vaoRender2,
Data1: buffer1,
Data2: buffer2,
ShapeData: shapeData,
NonTransformBuffer: nonTransformBuffer,
NumParticles: numParticles,
Origin: Origin,
Gravity: -9.81 / 200,
InitialSpeed: initialSpeed,
MaxLifetime: MaxLifetime,
}
min_h, max_h := w.HeightMap.Bounds()
W := float32(w.HeightMap.W)
H := float32(w.HeightMap.H)
TransformProg.Use()
ps.SetUniforms()
ps.SetVaos()
TransformProg.Use()
ps.TransformLoc.HeightMap.Uniform1i(constants.TextureHeightMap)
ps.TransformLoc.LowerBound.Uniform3f(0, 0, min_h)
ps.TransformLoc.UpperBound.Uniform3f(W, H, max_h)
return &ps
}