Refactor: move hitlist, object, sphere, viewport into single files.

Add bias_ctx for setting sub-pixel sampling bias.

1 files changed, 87 insertions, 0 deletions

diff --git a/viewport.h b/viewport.h
new file mode 100644
index 0000000..41c86a2
--- /dev/null
+++ b/viewport.h
@@ -0,0 +1,87 @@
+//
+// Created by Keuin on 2022/4/12.
+//
+
+#ifndef RT_VIEWPORT_H
+#define RT_VIEWPORT_H
+
+#include "timer.h"
+#include "bitmap.h"
+#include "ray.h"
+#include "vec.h"
+#include "hitlist.h"
+#include <cstdlib>
+#include <memory>
+#include <limits>
+#include <vector>
+#include <iostream>
+#include <cstdint>
+#include <random>
+
+// bias context, used for placing sub-pixels
+class bias_ctx {
+    bool enabled; // put all together, eliminating a virtual function call
+    std::mt19937_64 mt;
+    std::uniform_real_distribution<double> uni{0.0, 1.0};
+
+public:
+    bias_ctx(bool enabled, uint64_t seed = 0UL) : enabled(enabled), mt(std::mt19937_64{seed}) {}
+
+    void operator()(double &bx, double &by) {
+        if (enabled) {
+            bx = uni(mt);
+            by = uni(mt);
+        } else {
+            bx = 0.0;
+            by = 0.0;
+        }
+    }
+};
+
+class viewport {
+    const double half_width, half_height; // viewport size
+    const vec3d center; // coordinate of the viewport center point
+
+public:
+    viewport() = delete;
+
+    viewport(double width, double height, vec3d viewport_center) :
+            half_width(width / 2.0), half_height(height / 2.0), center(viewport_center) {}
+
+    /**
+     * Generate the image seen on given viewpoint.
+     * @param bx bias on x axis (0.0 <= bx < 1.0)
+     * @param by bias on y axis (0.0 <= by < 1.0)
+     * @return
+     */
+    bitmap8b render(const hitlist &world, vec3d viewpoint,
+                    uint16_t image_width, uint16_t image_height,
+                    bias_ctx &bias) const {
+        bitmap8b image{image_width, image_height};
+        double bx, by;
+        const auto r = center - viewpoint;
+        const int img_hw = image_width / 2, img_hh = image_height / 2;
+        // iterate over every pixel on the image
+        for (int j = -img_hh + 1; j <= img_hh; ++j) { // axis y, transformation is needed
+            for (int i = -img_hw; i < img_hw; ++i) { // axis x
+                bias(bx, by); // get a random bias (bx, by) for sub-pixel sampling
+                assert(0 <= bx);
+                assert(0 <= by);
+                assert(bx < 1.0);
+                assert(by < 1.0);
+                const vec3d off{
+                        .x=1.0 * i / img_hw * half_width + bx,
+                        .y=1.0 * j / img_hh * half_height + by,
+                        .z=0.0
+                }; // offset on screen plane
+                const auto dir = r + off; // direction vector from camera to current pixel on screen
+                const ray3d ray{viewpoint, dir}; // from camera to pixel (on the viewport)
+                const auto pixel = world.color(ray);
+                image.set(i + img_hw, -j + img_hh, pixel);
+            }
+        }
+        return image;
+    }
+};
+
+#endif //RT_VIEWPORT_H