From 4348cc9581bfea05359485c5d2d074132d0271da Mon Sep 17 00:00:00 2001
From: Julian T <julian@jtle.dk>
Date: Thu, 6 Aug 2020 19:21:49 +0200
Subject: Renders scenes with a single hardcoded light and green objects

---
 src/render.cpp | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 src/render.cpp

(limited to 'src/render.cpp')

diff --git a/src/render.cpp b/src/render.cpp
new file mode 100644
index 0000000..5601863
--- /dev/null
+++ b/src/render.cpp
@@ -0,0 +1,124 @@
+#include "render.hpp"
+#include "vector.hpp"
+#include "common.hpp"
+
+#include <math.h>
+#include <iostream>
+
+#define FOV 1.74533
+
+const Vec3d up = Vec3d(0, 1, 0);
+
+void Color::clamp() {
+    if (m_x > 1) { m_x = 1; }
+    if (m_y > 1) { m_y = 1; }
+    if (m_z > 1) { m_z = 1; }
+}
+
+Renderer::Renderer(const Scene &scn, Vec3d eye, Vec3d target, unsigned width, unsigned height) : 
+    m_scn(scn)
+{
+    m_eye = eye;
+    m_target = target;
+    m_width = width;
+    m_height = height;
+
+    recalculate();
+}
+
+void Renderer::recalculate() {
+    auto tmp = m_target - m_eye;
+
+    // Orthogonal vector to E
+    auto b = up.cross(tmp);
+
+    b.normalize();
+    tmp.normalize();
+
+    auto v = tmp.cross(b);
+
+    // Calculate size of viewplane
+    double gx = tan( FOV / 2);
+    double gy = gx * ((double) m_height / m_width);
+
+    // Calculate scaling vectors
+    m_qx = b * ((2 * gx) / (m_width - 1));
+    m_qy = v * ((2 * gy) / (m_height - 1));
+
+    // Calculate starting point
+    m_blc = tmp - (b * gx) - (v * gy);
+}
+
+Ray Renderer::findray(double x, double y) const {
+    auto dir = m_blc + (m_qx * x) + (m_qy * y);
+    return Ray(m_eye, dir, true);
+}
+
+Color Renderer::render(unsigned x, unsigned y) {
+    auto r = findray(x, y);
+    return pathtrace_sample(r, 0);
+}
+
+Color Renderer::pathtrace_sample(const Ray &r, unsigned hop) {
+    double dist;
+    auto res = cast_ray(r, 0, &dist);
+
+    if (!res) {
+        return Color(0, 0, 0);
+    }
+
+    // Calculate endpoint
+    auto end = r.m_start + r.m_direction * dist;
+
+    auto norm = res->norm_at(end, r.m_direction);
+
+    // Simulate single light
+    auto l = Vec3d(0, 7, 0);
+
+    auto tolight = l - end;
+    auto distance = tolight.length();
+    tolight.normalize();
+    auto lightray = Ray(end, tolight, false);
+
+    if (cast_ray(lightray, distance, nullptr)) {
+        return Color(0, 0, 0);
+    }
+
+    auto green = Color(0, 1, 0);
+    return Color(green * norm.dot(tolight));
+}
+
+const Shape* Renderer::cast_ray(const Ray &r, double chk_dist, double *dist_ret) {
+    const Shape *smallest = nullptr;
+    double dist = 0;
+
+    for (auto obj : m_scn.objs) {
+        if (!obj) {
+            continue;
+        }
+        auto d = obj->intersect(r, false);
+        if (d > ZERO_APPROX) {
+            if (chk_dist > 0 && d < chk_dist) {
+                dist = d; smallest = obj;
+                goto exit;
+            }
+            if (d < dist || smallest == nullptr) {
+                dist = d; smallest = obj;
+            }
+        }
+    }
+
+    if (chk_dist > 0) {
+        // If we reach this it means none of the
+        // object where within distance.
+        return nullptr;
+    }
+
+exit:
+
+    if (dist_ret) {
+        *dist_ret = dist;
+    }
+
+    return smallest;
+}
-- 
cgit v1.2.3