fixed perspective calculations

1 files changed, 70 insertions, 46 deletions

diff --git a/src/renderer.cpp b/src/renderer.cpp
index a946ce3..6e170f3 100644
--- a/src/renderer.cpp
+++ b/src/renderer.cpp
@@ -5,12 +5,14 @@
 #include <memory>
 #include "math/vector.h"
 #include "o3d/vertex.h"
+#include "o3d/deriv_vertex.h"
 #include "o3d/tri_vertex.h"
+#include "o3d/tri_deriv_vertex.h"
 #include "o3d/vertex_data.h"
 
 using namespace engine;
 
-Renderer::Renderer(std::unique_ptr<engine::fb::FrameBuffer> fb) : fb{std::move(fb)} {
+Renderer::Renderer(std::unique_ptr<fb::FrameBuffer> fb) : fb{std::move(fb)} {
     depth_buf.resize(this->fb->width() * this->fb->height());
 }
 
@@ -33,33 +35,36 @@ void Renderer::clear() {
     fb->clear();
 }
 
-void Renderer::_draw_cropped_triangle(engine::o3d::TriangleVertex3 triangle) {
-    std::array<engine::o3d::Vertex3*, 3> sorted_vs = { &triangle.vertex1, &triangle.vertex2, &triangle.vertex3 };
+void Renderer::_draw_cropped_triangle(o3d::TriangleVertex4 root, o3d::TriangleDerivedVertex4 triangle) {
+    std::array<o3d::DerivedVertex4*, 3> sorted_vs = { &triangle.derived_vertex1, &triangle.derived_vertex2, &triangle.derived_vertex3 };
 
-#define SWAP_IF_LT(X,Y) ({\
-            if (sorted_vs[X]->point.y < sorted_vs[Y]->point.y) {\
-                engine::o3d::Vertex3* temp = sorted_vs[X];\
-                sorted_vs[X] = sorted_vs[Y];\
-                sorted_vs[Y] = temp;\
-            }\
+#define SWAP_IF_LT(X,Y) ({ \
+            if (sorted_vs[X]->point.y < sorted_vs[Y]->point.y) { \
+                auto temp = sorted_vs[X]; \
+                sorted_vs[X] = sorted_vs[Y]; \
+                sorted_vs[Y] = temp; \
+            } \
         })
     SWAP_IF_LT(1, 0);
     SWAP_IF_LT(2, 1);
     SWAP_IF_LT(1, 0);
 #undef SWAP_IF_LT
 
-    engine::o3d::Vertex3 middle_vl = *sorted_vs[1];
-    float fac = (sorted_vs[1]->point.y - sorted_vs[0]->point.y) / (sorted_vs[2]->point.y - sorted_vs[0]->point.y);
-    engine::o3d::Vertex3 middle_vr{
+    auto middle_vl = *sorted_vs[1];
+    const float fac = (sorted_vs[1]->point.y - sorted_vs[0]->point.y) / (sorted_vs[2]->point.y - sorted_vs[0]->point.y);
+    const float fac_b0 = (1.f - fac) / sorted_vs[0]->point.w / ((1.f - fac) / sorted_vs[0]->point.w + fac / sorted_vs[2]->point.w);
+    o3d::DerivedVertex4 middle_vr{
         {
             sorted_vs[0]->point.x + fac * (sorted_vs[2]->point.x - sorted_vs[0]->point.x),
             sorted_vs[1]->point.y,
-            sorted_vs[0]->point.z + fac * (sorted_vs[2]->point.z - sorted_vs[0]->point.z)
+            fac_b0 * sorted_vs[0]->point.z + (1.f - fac_b0) * sorted_vs[2]->point.z,
+            1.f / (1.f / sorted_vs[0]->point.w + fac * (1.f / sorted_vs[2]->point.w - 1.f / sorted_vs[0]->point.w))
         },
-        engine::o3d::VertexData::lerp(sorted_vs[0]->data, sorted_vs[2]->data, fac)
+        sorted_vs[0]->b0 + fac * (sorted_vs[2]->b0 - sorted_vs[0]->b0),
+        sorted_vs[0]->b1 + fac * (sorted_vs[2]->b1 - sorted_vs[0]->b1)
     };
     if (middle_vr.point.x < middle_vl.point.x) {
-        engine::o3d::Vertex3 temp = middle_vr;
+        auto temp = middle_vr;
         middle_vr = middle_vl;
         middle_vl = temp;
     }
@@ -72,6 +77,7 @@ void Renderer::_draw_cropped_triangle(engine::o3d::TriangleVertex3 triangle) {
             for (int y = top_y; y <= bottom_y; y++) {
                 float iy = static_cast<float>(y);
                 float s = (iy - sorted_vs[0]->point.y) / (sorted_vs[1]->point.y - sorted_vs[0]->point.y);
+                float sub_bb0 = 1.f - s;
                 float xl = sorted_vs[0]->point.x + s * (middle_vl.point.x - sorted_vs[0]->point.x);
                 float xr = sorted_vs[0]->point.x + s * (middle_vr.point.x - sorted_vs[0]->point.x);
                 int left_x = static_cast<int>(std::ceil(xl));
@@ -79,13 +85,23 @@ void Renderer::_draw_cropped_triangle(engine::o3d::TriangleVertex3 triangle) {
                 for (int x = left_x; x <= right_x; x++) {
                     float ix = static_cast<float>(x);
                     float t = (ix - xl) / (xr - xl);
-                    // depth and vd don't take into account perspective
-                    float u = s, v = t;
-                    float depth = sorted_vs[0]->point.z + u * (middle_vl.point.z - sorted_vs[0]->point.z + v * (middle_vr.point.z - middle_vl.point.z));
-                    if (depth < depth_buf[x + y * fb->width()]) {
-                        depth_buf[x + y * fb->width()] = depth;
-                        fb->draw_point(x, y, engine::math::Vector3{static_cast<float>(face_ind) + .5f, 0.f, 0.f},
-                            engine::o3d::VertexData::bilerp(sorted_vs[0]->data, middle_vl.data, middle_vr.data, u, v));
+                    float sub_bb1 = s * (1.f - t);
+                    float b_fac = 1.f / (
+                        sub_bb0 / sorted_vs[0]->point.w
+                        + sub_bb1 / middle_vl.point.w
+                        + (1.f - sub_bb0 - sub_bb1) / middle_vr.point.w);
+                    float sub_b0 = b_fac * sub_bb0 / sorted_vs[0]->point.w;
+                    float sub_b1 = b_fac * sub_bb1 / middle_vl.point.w;
+                    math::Vector3 loc{
+                        sub_b0 * sorted_vs[0]->point.x + sub_b1 * middle_vl.point.x + (1.f - sub_b0 - sub_b1) * middle_vr.point.x,
+                        sub_b0 * sorted_vs[0]->point.y + sub_b1 * middle_vl.point.y + (1.f - sub_b0 - sub_b1) * middle_vr.point.y,
+                        sub_b0 * sorted_vs[0]->point.z + sub_b1 * middle_vl.point.z + (1.f - sub_b0 - sub_b1) * middle_vr.point.z
+                    };
+                    if (loc.z < depth_buf[x + y * fb->width()]) {
+                        depth_buf[x + y * fb->width()] = loc.z;
+                        fb->draw_point(x, y, loc, o3d::VertexData::bilerp(root.vertex1.data, root.vertex2.data, root.vertex3.data,
+                            sub_b0 * sorted_vs[0]->b0 + sub_b1 * middle_vl.b0 + (1.f - sub_b0 - sub_b1) * middle_vr.b0,
+                            sub_b0 * sorted_vs[0]->b1 + sub_b1 * middle_vl.b1 + (1.f - sub_b0 - sub_b1) * middle_vr.b1));
                     }
                 }
             }
@@ -100,6 +116,7 @@ void Renderer::_draw_cropped_triangle(engine::o3d::TriangleVertex3 triangle) {
             for (int y = top_y; y <= bottom_y; y++) {
                 float iy = static_cast<float>(y);
                 float s = (iy - sorted_vs[2]->point.y) / (sorted_vs[1]->point.y - sorted_vs[2]->point.y);
+                float sub_bb0 = 1.f - s;
                 float xl = sorted_vs[2]->point.x + s * (middle_vl.point.x - sorted_vs[2]->point.x);
                 float xr = sorted_vs[2]->point.x + s * (middle_vr.point.x - sorted_vs[2]->point.x);
                 int left_x = static_cast<int>(std::ceil(xl));
@@ -107,13 +124,23 @@ void Renderer::_draw_cropped_triangle(engine::o3d::TriangleVertex3 triangle) {
                 for (int x = left_x; x <= right_x; x++) {
                     float ix = static_cast<float>(x);
                     float t = (ix - xl) / (xr - xl);
-                    // depth and vd don't take into account perspective
-                    float u = s, v = t;
-                    float depth = sorted_vs[2]->point.z + u * (middle_vl.point.z - sorted_vs[2]->point.z + v * (middle_vr.point.z - middle_vl.point.z));
-                    if (depth < depth_buf[x + y * fb->width()]) {
-                        depth_buf[x + y * fb->width()] = depth;
-                        fb->draw_point(x, y, engine::math::Vector3{static_cast<float>(face_ind) + .5f, 0.f, 0.f},
-                            engine::o3d::VertexData::bilerp(sorted_vs[2]->data, middle_vl.data, middle_vr.data, u, v));
+                    float sub_bb1 = s * (1.f - t);
+                    float b_fac = 1.f / (
+                        sub_bb0 / sorted_vs[2]->point.w
+                        + sub_bb1 / middle_vl.point.w
+                        + (1.f - sub_bb0 - sub_bb1) / middle_vr.point.w);
+                    float sub_b0 = b_fac * sub_bb0 / sorted_vs[2]->point.w;
+                    float sub_b1 = b_fac * sub_bb1 / middle_vl.point.w;
+                    math::Vector3 loc{
+                        sub_b0 * sorted_vs[2]->point.x + sub_b1 * middle_vl.point.x + (1.f - sub_b0 - sub_b1) * middle_vr.point.x,
+                        sub_b0 * sorted_vs[2]->point.y + sub_b1 * middle_vl.point.y + (1.f - sub_b0 - sub_b1) * middle_vr.point.y,
+                        sub_b0 * sorted_vs[2]->point.z + sub_b1 * middle_vl.point.z + (1.f - sub_b0 - sub_b1) * middle_vr.point.z
+                    };
+                    if (loc.z < depth_buf[x + y * fb->width()]) {
+                        depth_buf[x + y * fb->width()] = loc.z;
+                        fb->draw_point(x, y, loc, o3d::VertexData::bilerp(root.vertex1.data, root.vertex2.data, root.vertex3.data,
+                            sub_b0 * sorted_vs[2]->b0 + sub_b1 * middle_vl.b0 + (1.f - sub_b0 - sub_b1) * middle_vr.b0,
+                            sub_b0 * sorted_vs[2]->b1 + sub_b1 * middle_vl.b1 + (1.f - sub_b0 - sub_b1) * middle_vr.b1));
                     }
                 }
             }
@@ -121,25 +148,22 @@ void Renderer::_draw_cropped_triangle(engine::o3d::TriangleVertex3 triangle) {
     }
 }
 
-void Renderer::draw_triangle(engine::o3d::TriangleVertex4 triangle) {
+void Renderer::draw_triangle(o3d::TriangleVertex4 triangle) {
     face_ind++;
-    for (auto t1 : triangle.crop_z_out(-1.f, 1.f)) {
-        for (auto t2 : t1.div_by_w().crop_xy_out(-1.f, 1.f, -1.f, 1.f)) {
-            engine::math::Vector2 pp1 = t2.vertex1.point.xy(),
-                                      pp2 = t2.vertex2.point.xy(),
-                                      pp3 = t2.vertex3.point.xy();
+    for (auto t1 : triangle.to_derived().crop_z_out(-1.f, 1.f)) {
+        for (auto t2 : t1.div_by_w().perspective_crop_xy_out(-1.f, 1.f, -1.f, 1.f)) {
+            math::Vector2 pp1 = t2.derived_vertex1.point.xy();
+            math::Vector2 pp2 = t2.derived_vertex2.point.xy();
+            math::Vector2 pp3 = t2.derived_vertex3.point.xy();
             if ((pp2 - pp1).det(pp3 - pp1) >= 0.f) continue;
-            t2.vertex1.point = (t2.vertex1.point + engine::math::Vector3{1.f, 1.f, 0.f}) / 2.f;
-            t2.vertex2.point = (t2.vertex2.point + engine::math::Vector3{1.f, 1.f, 0.f}) / 2.f;
-            t2.vertex3.point = (t2.vertex3.point + engine::math::Vector3{1.f, 1.f, 0.f}) / 2.f;
-            float fw = static_cast<float>(fb->width()), fh = static_cast<float>(fb->height());
-            t2.vertex1.point.x = t2.vertex1.point.x * fw - .5f;
-            t2.vertex1.point.y = t2.vertex1.point.y * fh - .5f;
-            t2.vertex2.point.x = t2.vertex2.point.x * fw - .5f;
-            t2.vertex2.point.y = t2.vertex2.point.y * fh - .5f;
-            t2.vertex3.point.x = t2.vertex3.point.x * fw - .5f;
-            t2.vertex3.point.y = t2.vertex3.point.y * fh - .5f;
-            _draw_cropped_triangle(t2);
+            float fw_over_2 = static_cast<float>(fb->width()) / 2.f, fh_over_2 = static_cast<float>(fb->height()) / 2.f;
+            t2.derived_vertex1.point.x = (t2.derived_vertex1.point.x + 1.f) * fw_over_2 - .5f;
+            t2.derived_vertex1.point.y = (t2.derived_vertex1.point.y + 1.f) * fh_over_2 - .5f;
+            t2.derived_vertex2.point.x = (t2.derived_vertex2.point.x + 1.f) * fw_over_2 - .5f;
+            t2.derived_vertex2.point.y = (t2.derived_vertex2.point.y + 1.f) * fh_over_2 - .5f;
+            t2.derived_vertex3.point.x = (t2.derived_vertex3.point.x + 1.f) * fw_over_2 - .5f;
+            t2.derived_vertex3.point.y = (t2.derived_vertex3.point.y + 1.f) * fh_over_2 - .5f;
+            _draw_cropped_triangle(triangle, t2);
         }
     }
 }