Correct for perspective in texturing

spec/line_spec.cr

@@ -0,0 +1,7 @@
+require "./spec_helper"
+require "../src/line"
+
+include PF
+
+describe Line do
+end

spec/vector_spec.cr

@@ -70,6 +70,11 @@ describe Vector do
       v1 = Vector[5, 5]
       (v1 // 2).should eq(Vector[2, 2])
     end
+
+    it "applies exponents" do
+      v = Vector[2, 2] ** 5
+      v.should eq(Vector[32, 32])
+    end
   end
 
   describe "#-" do
@@ -80,6 +85,13 @@ describe Vector do
     end
   end
 
+  describe "#sum" do
+    it "returns all components added together" do
+      v = Vector[1, 2, 3]
+      v.sum.should eq(6)
+    end
+  end
+
   describe "#abs" do
     it "returns the absolute value" do
       v = Vector[-1, -1]

src/3d/mesh.cr

@@ -23,12 +23,17 @@ module PF
           parts = line.split(/\s+/)
 
           case parts[0]
+          when "o"
+            puts "Object: #{parts[1]}"
+            # TODO: This is when a new mesh starts
+          when "mtllib"
+            # TODO This is where we need to load texture and material information
           when "v"
             w = parts[4]?.try { |n| n.to_f64 }
             verticies << Vector3.new(x: parts[1].to_f64, y: parts[2].to_f64, z: parts[3].to_f64)
           when "vt"
             v = parts[2]?.try { |n| n.to_f64 } || 0.0
-            w = parts[3]?.try { |n| n.to_f64 } || 0.0
+            w = parts[3]?.try { |n| n.to_f64 } || 1.0
             texture_verticies << Vector3.new(parts[1].to_f64, v, w)
           when "vn"
             if use_normals
@@ -67,9 +72,13 @@ module PF
             tris << tri
 
             # Split a square into triangles
-            # TODO: Handle texture points
             if face_verts.size > 3
               tri = Tri.new(face_verts[0], face_verts[2], face_verts[3], normal: normal)
+              unless face_tex.empty?
+                tri.t1 = face_tex[0]
+                tri.t2 = face_tex[2]
+                tri.t3 = face_tex[3]
+              end
               tris << tri
             end
           end

src/3d/tri.cr

@@ -48,15 +48,19 @@ module PF
 
     # Multiply all points by a *Matrix*, returning a new *Tri*
     def *(mat : Matrix)
+      # The transform function returns a w, which is the 4th component of the vertex
+      # this is the perspective information that we can use to apply textures
       pp1, w1 = Transform3d.apply(@p1, mat)
       pp2, w2 = Transform3d.apply(@p2, mat)
       pp3, w3 = Transform3d.apply(@p3, mat)
 
+      pt1 = @t1 / w1
+      pt2 = @t2 / w2
+      pt3 = @t3 / w3
+
       Tri.new(
         pp1, pp2, pp3,
-        @t1,
-        @t2,
-        @t3,
+        pt1, pt2, pt3,
         @color
       )
     end

src/line.cr

@@ -2,9 +2,9 @@ require "./vector"
 
 module PF
   struct Line(T)
-    property p1 : Vector2(T), p2 : Vector2(T)
+    property p1 : T, p2 : T
 
-    def initialize(@p1 : Vector2(T), @p2 : Vector2(T))
+    def initialize(@p1 : T, @p2 : T)
     end
 
     def rise
@@ -66,16 +66,18 @@ module PF
       (@p2 - @p1) * t + @p1
     end
 
+    # Return the length of the line
     def length
-      Math.sqrt((run.abs * 2) + (rise.abs * 2))
+      Math.sqrt(((@p2 - @p1) ** 2).sum)
     end
 
     def /(n : (Float | Int))
       Line.new(@p1 / n, @p2 / n)
     end
 
-    def to_point
-      Vector[run, rise]
+    # Convert this line into a normalized vector
+    def to_vector
+      (@p2 - @p1).normalized
     end
 
     # Find the normal axis to this line

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 : Vector2, t2 : Vector2, t3 : Vector2, sprite : Sprite, color : Pixel = Pixel.white)
+    def fill_triangle(p1 : Vector2, p2 : Vector2, p3 : Vector2, t1 : Vector3, t2 : Vector3, t3 : Vector3, sprite : Sprite, 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
@@ -114,6 +114,7 @@ module PF
 
         # Get the normalized t value for this height level
         ty = height > 0 ? y / height : 0.0
+
         # LERP both texture edges at the y position to create a new line
         tyl =
           if switch_left
@@ -148,10 +149,14 @@ module PF
         x_left.upto(x_right) do |x|
           # LERP the line between the texture edges
           t = scan_size == 0 ? 0.0 : (x - x_left) / scan_size
-          # Multiply the point by the size of the sprite to get the final texture point
-          sample_point = texture_line.lerp(t) * sprite.size
-          pixel = sprite.sample((sample_point + 0.5).to_i)
+          texture_point = texture_line.lerp(t)
 
+          # 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)
+
+          # Blend the pixel sample with the provided color
           pixel.r = (pixel.r * (color.r / 255)).to_u8
           pixel.g = (pixel.g * (color.g / 255)).to_u8
           pixel.b = (pixel.b * (color.b / 255)).to_u8

src/vector.cr

@@ -1,7 +1,7 @@
 require "./matrix"
 
 module PF
-  module Vector
+  abstract struct Vector
     # Creates a new `Vector` with the given *args*
     #
     # ```
@@ -18,7 +18,7 @@ module PF
 
   {% for i in 2..4 %}
     {% vars = %w[x y z w] %}
-    struct Vector{{i}}(T)
+    struct Vector{{i}}(T) < Vector
       {% for arg in 0...i %}
         property {{vars[arg].id}} : T
       {% end %}
@@ -64,7 +64,7 @@ module PF
         end
       {% end %}
 
-      {% for op in %w[* / // + - %] %}
+      {% for op in %w[* / // + - % **] %}
         # Applies `{{op.id}}` to all component of this vector with the corresponding component of *other*
         def {{ op.id }}(other : Vector{{i}})
           Vector[{% for arg in 0...i %} @{{vars[arg].id}} {{op.id}} other.{{vars[arg].id}}, {% end %}]
@@ -76,6 +76,13 @@ module PF
         end
       {% end %}
 
+      # Add all components together
+      def sum
+        {% for arg in 0...i %}
+          @{{vars[arg].id}} {% if arg != i - 1 %} + {% end %}
+        {% end %}
+      end
+
       # The length or magnitude of the vector calculated by the Pythagorean theorem
       def magnitude
         Math.sqrt({% for arg in 0...i %} @{{vars[arg].id}} ** 2 {% if arg != i - 1 %} + {% end %}{% end %})