I've been using vectors to determine the points of a triangle of which to draw, I have seen a good bit of the basis part of the series and have done a min max rectangle to limit the portion of the screen to check pixels if they are inside the three vector points.

I've done several methods, checking which side the point is on relative to every vector, I've done a Barycentric method, and a couple others. The one I'm currently using seems fit as it doesn't care if the points go clockwise or counter-clockwise.

The bug comes in when it creates a weird monstrosity triangle like the one

[attachment=43]triangles.png[/attachment]. The purple squares are centered on the point where a vector point is at.

These are the three vectors that are represented by the purple squares

1 2 3 | v2 test_v1 = {100, 100}; v2 test_v2 = {150, 100}; v2 test_v3 = {125, 150}; |

This is a method of seeing if a point is within three vector points.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | inline bool32 IsInTriangle(v2 p, v2 p0, v2 p1, v2 p2) { bool32 result = false; v2 temp0 = p2 - p0; v2 temp1 = p1 - p0; v2 temp2 = p - p0; float dot00 = Dot(temp0, temp0); float dot01 = Dot(temp0, temp1); float dot02 = Dot(temp0, temp2); float dot11 = Dot(temp1, temp1); float dot12 = Dot(temp1, temp2); float inv = 1 / (dot00 * dot11 - dot01 * dot01); float u = (dot11 * dot02 - dot01 * dot12) * inv; float v = (dot00 * dot12 - dot01 * dot02) * inv; result = (u >= 0) && (v >= 0) && (u + v < 1); return result; } |

and then the triangle rendering function that writes the pixel data to the pixel buffer

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | local void TestRender(Game_Screen_Buffer *buffer, v2 p0 , v2 p1, v2 p2, uint8 r, uint8 g, uint8 b, uint8 a = 255) { float inner_min_x = Min(p0.x, p1.x); float inner_max_x = Max(p0.x, p1.x); float inner_min_y = Min(p0.y, p1.y); float inner_max_y = Max(p0.y, p1.y); float min_x = Min(inner_min_x, p2.x); float max_x = Max(inner_max_x, p2.x); float min_y = Min(inner_min_y, p2.y); float max_y = Max(inner_max_y, p2.y); if(min_x < 0.0f) { min_x = 0.0f; } if(min_y < 0.0f) { min_y = 0.0f; } if(max_x > buffer->width) { max_x = (float)buffer->width; } if(max_y > buffer->height) { max_y = (float)buffer->height; } #if 1 Rectangle(buffer, (int32)p0.x - 3, (int32)p0.y - 3, 6, 6, 255, 0, 255); Rectangle(buffer, (int32)p1.x - 3, (int32)p1.y - 3, 6, 6, 255, 0, 255); Rectangle(buffer, (int32)p2.x - 3, (int32)p2.y - 3, 6, 6, 255, 0, 255); #else Rectangle(buffer, (int32)min_x - 3, (int32)min_y - 3, 6, 6, 255, 255, 0); Rectangle(buffer, (int32)min_x - 3, (int32)max_y - 3, 6, 6, 255, 255, 0); Rectangle(buffer, (int32)max_x - 3, (int32)min_y - 3, 6, 6, 255, 255, 0); Rectangle(buffer, (int32)max_x - 3, (int32)max_y - 3, 6, 6, 255, 255, 0); #endif uint32 blue = (uint32)b; uint32 green = (uint32)g; uint32 red = (uint32)r; uint32 alpha = (uint32)a; uint32 color = ((alpha << 24) | (red << 16) | (green << 8) | blue); uint8 *pitch = ((uint8 *)buffer->memory + (int32)min_x * buffer->bytes_per_pixel + (int32)min_y * buffer->pitch); for(float y = min_y; y < max_y; ++y) { uint32 *pixel = (uint32 *)pitch; for(float x = min_x; x < max_x; ++x) { if(IsInTriangle(V2(x, y), p0, p1, p2)) { *pixel++ = color; } } pitch += buffer->pitch; } } |

I'm not really sure whats going on honestly, I think I might have screwed up the dot products somehow, but they all look okay to me, though Any method that's worked produces the same problem so maybe It has to do with getting pixels in the pixel buffer?