Add depth buffer

src/3d/depth_buffer.cr

@@ -0,0 +1,24 @@
+module PF
+  # A buffer of depth values for rending 3d scenes
+  class DepthBuffer
+    @values : Slice(Float64)
+    @width : Int32
+    @height : Int32
+
+    def initialize(@width, @height)
+      @values = Slice(Float64).new(@width * @height, 0.0)
+    end
+
+    def clear
+      @values.fill(0.0)
+    end
+
+    def [](x : Int, y : Int)
+      @values[y * @width + x]
+    end
+
+    def []=(x : Int, y : Int, value : Float64)
+      @values[y * @width + x] = value
+    end
+  end
+end

src/3d/projector.cr

@@ -55,7 +55,7 @@ module PF
     end
 
     # Project an array of Triangles into screen space
-    def project(tris : Array(Tri), camera = @camera)
+    def project(tris : Array(Tri), camera = @camera, sort : Bool = false)
       mat_view = camera.view_matrix
 
       # only draw triangles facing the camera
@@ -96,9 +96,8 @@ module PF
         end
       end
 
-      # sort triangles
-      # TODO: Z-buffer
-      tris.sort! { |a, b| b.z <=> a.z }
+      # sort triangles, no need to do this if using a depth buffer
+      tris.sort! { |a, b| b.z <=> a.z } if sort
 
       # Clip against the edges of the screen
       {

src/sprite/fill_triangle.cr

@@ -61,7 +61,7 @@ module PF
     end
 
     # Draw a textured triangle
-    def fill_triangle(p1 : Vector2, p2 : Vector2, p3 : Vector2, t1 : Vector3, t2 : Vector3, t3 : Vector3, sprite : Sprite, color : Pixel = Pixel.white)
+    def fill_triangle(p1 : Vector2, p2 : Vector2, p3 : Vector2, t1 : Vector3, t2 : Vector3, t3 : Vector3, sprite : Sprite, buffer : DepthBuffer, color : Pixel = Pixel.white)
       # Sort points from top to bottom
       p1, p2, t1, t2 = p2, p1, t2, t1 if p2.y < p1.y
       p1, p3, t1, t3 = p3, p1, t3, t1 if p3.y < p1.y
@@ -151,10 +151,15 @@ module PF
           t = scan_size == 0 ? 0.0 : (x - x_left) / scan_size
           texture_point = texture_line.lerp(t)
 
+          if texture_point.z >= buffer[x, y + c]
+            buffer[x, y + c] = texture_point.z
             # Get the x and y of the texture coords, divide by z for perspective, then
             # multiply the point by the size of the sprite to get the final texture point
-          sample_point = Vector[texture_point.x / texture_point.z, texture_point.y / texture_point.z] * sprite.size
-          pixel = sprite.sample(sample_point.to_i)
+            sample_point = ((Vector[texture_point.x, texture_point.y] / texture_point.z) * sprite.size)
+            # Invert the y axis for the sprite
+            sample_point.y = sprite.height - sample_point.y
+            # sample_point = sample_point / texture_point.z if texture_point.z != 0
+            pixel = sprite.sample((sample_point + 0.5).to_i)
 
             # Blend the pixel sample with the provided color
             pixel.r = (pixel.r * (color.r / 255)).to_u8
@@ -163,6 +168,7 @@ module PF
 
             draw_point(x, y + c, pixel)
           end
+        end
 
         # Once we hit the point where a line changes, we need a new slope for that line
         if y == mid