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SurfaceMesh.cs
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SurfaceMesh.cs
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using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
namespace Microsoft.Xna.Framework
{
/// <summary>
/// Will Motill 2016. - 2018
/// This class provides methods to build indexed triangle meshes from a grid of positional points.
/// It also provides the ability to create smooth normals and generate simple tangents for normal mapping.
/// </summary>
public class SurfaceMesh
{
public bool showConsoleInfo = false;
public bool invertXtextureCoordinatesCreation = false;
public bool invertYtextureCoordinatesCreation = true;
public bool invertNormalsOnCreation = false;
int surfacePointWidth = 0;
public VertexPositionNormalTextureTangent[] vertices;
public int[] indices;
public void CreateSurfaceMesh(Vector4[] inputSurfaceVectors, int w, int h)
{
surfacePointWidth = w;
indices = SetUpIndices(w, h);
vertices = VertexFromVectorArray(w, h, inputSurfaceVectors);
vertices = CreateSmoothNormals(vertices, indices);
CreateTangents();
}
public void CreateSurfaceMesh(Vector4[] inputSurfaceVectors, int w, int h, out VertexPositionNormalTextureTangent[] verts, out int[] indexs)
{
surfacePointWidth = w;
indices = SetUpIndices(w, h);
vertices = VertexFromVectorArray(w, h, inputSurfaceVectors);
vertices = CreateSmoothNormals(vertices, indices);
CreateTangents();
verts = vertices;
indexs = indices;
}
public Vector4[] Vector4FromVector3Array(Vector3[] inputSurfaceVectors)
{
var len = inputSurfaceVectors.Length;
Vector4[] vector4_surface_pos_ary = new Vector4[len];
for (int i = 0; i < inputSurfaceVectors.Length; i++)
{
vector4_surface_pos_ary[i] = new Vector4(
inputSurfaceVectors[i].X,
inputSurfaceVectors[i].Y,
inputSurfaceVectors[i].Z,
1f
);
}
return vector4_surface_pos_ary;
}
int[] SetUpIndices(int w, int h)
{
int counter = 0;
indices = new int[(w - 1) * (h - 1) * 6];
for (int y = 0; y < h - 1; y++)
{
for (int x = 0; x < w - 1; x++)
{
int topLeft = x + (y + 1) * w;
int topRight = (x + 1) + (y + 1) * w;
int lowerRight = (x + 1) + y * w;
int lowerLeft = x + y * w;
indices[counter++] = (int)topLeft;
indices[counter++] = (int)lowerRight;
indices[counter++] = (int)lowerLeft;
indices[counter++] = (int)topLeft;
indices[counter++] = (int)topRight;
indices[counter++] = (int)lowerRight;
}
}
return indices;
}
/// <summary>
/// Couldn't really decide if i wanted this method to be public or not.
/// </summary>
VertexPositionNormalTextureTangent[] VertexFromVectorArray(int verts_width, int verts_height, Vector4[] inputSurfaceVectors)
{
surfacePointWidth = verts_width;
VertexPositionNormalTextureTangent[] MyMeshVertices = new VertexPositionNormalTextureTangent[verts_width * verts_height];
vertices = new VertexPositionNormalTextureTangent[verts_width * verts_height];
for (int y = 0; y < verts_height; y++)
{
for (int x = 0; x < verts_width; x++)
{
int index = x + y * verts_width;
float u = (float)x / (verts_width - 1);
float v = (float)y / (verts_height - 1);
if (invertXtextureCoordinatesCreation) { u = 1f - u; }
if (invertYtextureCoordinatesCreation) { v = 1f - v; }
var tmp = inputSurfaceVectors[index];
Vector3 vec = new Vector3(tmp.X, tmp.Y, tmp.Z);
MyMeshVertices[index].Position = vec;
MyMeshVertices[index].TextureCoordinate.X = u;
MyMeshVertices[index].TextureCoordinate.Y = v;
}
}
return MyMeshVertices;
}
/// <summary>
/// This method creates smoothed normals from a indexed vertice mesh array.
/// This loops thru the index array finding the each triangle connected to a vertice.
/// It then calculates the normal for those triangles and averages them for the vertice in question.
/// This method can deal with abritrary numbers of connected triangles 0 to n connections.
/// </summary>
VertexPositionNormalTextureTangent[] CreateSmoothNormals(VertexPositionNormalTextureTangent[] vertices, int[] indexs)
{
// For each vertice we must calculate the surrounding triangles normals, average them and set the normal.
int tvertmultiplier = 3;
int triangles = (int)(indexs.Length / tvertmultiplier);
for (int currentTestedVerticeIndex = 0; currentTestedVerticeIndex < vertices.Length; currentTestedVerticeIndex++)
{
Vector3 sum = Vector3.Zero;
float total = 0;
for (int t = 0; t < triangles; t++)
{
int tvstart = t * tvertmultiplier;
int tindex0 = tvstart + 0;
int tindex1 = tvstart + 1;
int tindex2 = tvstart + 2;
var vindex0 = indices[tindex0];
var vindex1 = indices[tindex1];
var vindex2 = indices[tindex2];
if (vindex0 == currentTestedVerticeIndex || vindex1 == currentTestedVerticeIndex || vindex2 == currentTestedVerticeIndex)
{
var n0 = (vertices[vindex1].Position - vertices[vindex0].Position) * 10f; // * 10 math artifact avoidance.
var n1 = (vertices[vindex2].Position - vertices[vindex1].Position) * 10f;
var cnorm = Vector3.Cross(n0, n1);
sum += cnorm;
total += 1;
}
}
if (total > 0)
{
var averagednormal = sum / total;
averagednormal.Normalize();
if (invertNormalsOnCreation)
averagednormal = -averagednormal;
vertices[currentTestedVerticeIndex].Normal = averagednormal;
}
}
return vertices;
}
void CreateTangents()
{
for(int i = 0; i < vertices.Length;i++)
{
int y = i / surfacePointWidth;
int x = i - (y * surfacePointWidth);
int up = (y - 1) * surfacePointWidth + x;
int down = (y + 1) * surfacePointWidth + x;
Vector3 tangent = new Vector3();
if(down >= vertices.Length)
{
tangent = vertices[up].Position - vertices[i].Position;
tangent.Normalize();
vertices[i].Tangent = tangent;
}
else
{
tangent = vertices[i].Position - vertices[down].Position;
tangent.Normalize();
vertices[i].Tangent = tangent;
}
}
}
/// <summary>
/// Draws this surface mesh using user index primitives..
/// Doesn't set effect parameters or techniques.
/// </summary>
public void Draw(GraphicsDevice gd, Effect effect)
{
foreach (EffectPass pass in effect.CurrentTechnique.Passes)
{
pass.Apply();
gd.DrawUserIndexedPrimitives(PrimitiveType.TriangleList, vertices, 0, vertices.Length, indices, 0, (indices.Length / 3), VertexPositionNormalTextureTangent.VertexDeclaration);
}
}
public struct VertexPositionNormalTextureTangent : IVertexType
{
public Vector3 Position;
public Vector3 Normal;
public Vector2 TextureCoordinate;
public Vector3 Tangent;
public static VertexDeclaration VertexDeclaration = new VertexDeclaration
(
new VertexElement(VertexElementByteOffset.PositionStartOffset(), VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
new VertexElement(VertexElementByteOffset.OffsetVector3(), VertexElementFormat.Vector3, VertexElementUsage.Normal, 0),
new VertexElement(VertexElementByteOffset.OffsetVector2(), VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0),
new VertexElement(VertexElementByteOffset.OffsetVector3(), VertexElementFormat.Vector3, VertexElementUsage.Normal, 1)
);
VertexDeclaration IVertexType.VertexDeclaration { get { return VertexDeclaration; } }
}
/// <summary>
/// This is a helper struct for tallying byte offsets
/// </summary>
public struct VertexElementByteOffset
{
public static int currentByteSize = 0;
[STAThread]
public static int PositionStartOffset() { currentByteSize = 0; var s = sizeof(float) * 3; currentByteSize += s; return currentByteSize - s; }
public static int Offset(float n) { var s = sizeof(float); currentByteSize += s; return currentByteSize - s; }
public static int Offset(Vector2 n) { var s = sizeof(float) * 2; currentByteSize += s; return currentByteSize - s; }
public static int Offset(Color n) { var s = sizeof(int); currentByteSize += s; return currentByteSize - s; }
public static int Offset(Vector3 n) { var s = sizeof(float) * 3; currentByteSize += s; return currentByteSize - s; }
public static int Offset(Vector4 n) { var s = sizeof(float) * 4; currentByteSize += s; return currentByteSize - s; }
public static int OffsetFloat() { var s = sizeof(float); currentByteSize += s; return currentByteSize - s; }
public static int OffsetColor() { var s = sizeof(int); currentByteSize += s; return currentByteSize - s; }
public static int OffsetVector2() { var s = sizeof(float) * 2; currentByteSize += s; return currentByteSize - s; }
public static int OffsetVector3() { var s = sizeof(float) * 3; currentByteSize += s; return currentByteSize - s; }
public static int OffsetVector4() { var s = sizeof(float) * 4; currentByteSize += s; return currentByteSize - s; }
}
}
}