// raytrace a pixel (ie, set pixel color to result of a trace of a ray starting from eye position and
// passing through the world coords of the pixel)
static Color RenderPixel(int x, int y) {
// First, calculate direction of the current pixel from eye position
number sx = screenTopLeftPos.x + (x * pixelWidth);
number sy = screenTopLeftPos.y - (y * pixelHeight);
Vector3f eyeToPixelDir = new Vector3f(sx, sy, 0) - eyePos;
eyeToPixelDir.Normalise();
// Set up primary (eye) ray
Ray ray = new Ray(eyePos, eyeToPixelDir);
// And trace it!
return Trace(ray, 0);
}
// given a ray, trace it into the scene and return the colour of the surface it hits
// (handles reflections recursively)
static Color Trace(Ray ray, int traceDepth) {
// See if the ray intersected an object
CheckIntersection(ref ray);
if (ray.closestHitDistance >= Ray.WORLD_MAX || ray.closestHitObject == null) // No intersection
return BG_COLOR;
// Got a hit - set initial colour to ambient light
number r = 0.15f * ray.closestHitObject.color.R;
number g = 0.15f * ray.closestHitObject.color.G;
number b = 0.15f * ray.closestHitObject.color.B;
// Set up stuff we'll need for shading calcs
Vector3f surfaceNormal = ray.closestHitObject.GetSurfaceNormalAtPoint(ray.hitPoint);
Vector3f viewerDir = -ray.direction; // Direction back to the viewer (simply negative of ray dir)
// Loop through the lights, adding contribution of each
foreach (Light light in lights) {
Vector3f lightDir = new Vector3f();
number lightDistance;
// Find light direction and distance
lightDir = light.position - ray.hitPoint; // Get direction to light
lightDistance = lightDir.Magnitude();
//lightDir = lightDir / lightDistance; // Light exponential falloff
lightDir.Normalise();
// Shadow check: check if this light's visible from the point
// NB: Step out slightly from the hitpoint first
Ray shadowRay = new Ray(ray.hitPoint + (lightDir * TINY), lightDir);
shadowRay.closestHitDistance = lightDistance; // IMPORTANT: We only want it to trace as far as the light!
CheckIntersection(ref shadowRay);
if (shadowRay.closestHitObject != null) // We hit something -- ignore this light entirely
continue;
number cosLightAngleWithNormal = surfaceNormal.Dot(lightDir);
if (MATERIAL_DIFFUSE_COEFFICIENT > TINY) {
// Calculate light's diffuse component - note that this is view independant
// Dot product of surface normal and light direction gives cos of angle between them so will be in
// range -1 to 1. We use that as a scaling factor; common technique, called "cosine shading".
if (cosLightAngleWithNormal <= 0) continue;
// Add this light's diffuse contribution to our running totals
r += MATERIAL_DIFFUSE_COEFFICIENT * cosLightAngleWithNormal * ray.closestHitObject.color.R;
g += MATERIAL_DIFFUSE_COEFFICIENT * cosLightAngleWithNormal * ray.closestHitObject.color.G;
b += MATERIAL_DIFFUSE_COEFFICIENT * cosLightAngleWithNormal * ray.closestHitObject.color.B;
}
if (MATERIAL_SPECULAR_COEFFICIENT > TINY) {
// Specular component - dot product of light's reflection vector and viewer direction
// Direction to the viewer is simply negative of the ray direction
Vector3f lightReflectionDir = surfaceNormal * (cosLightAngleWithNormal * 2) - lightDir;
number specularFactor = viewerDir.Dot(lightReflectionDir);
if (specularFactor > 0) {
// To get smaller, sharper highlights we raise it to a power and multiply it
specularFactor = MATERIAL_SPECULAR_COEFFICIENT * (number)Math.Pow(specularFactor, MATERIAL_SPECULAR_POWER);
// Add the specular contribution to our running totals
r += specularFactor * ray.closestHitObject.color.R;
g += specularFactor * ray.closestHitObject.color.G;
b += specularFactor * ray.closestHitObject.color.B;
}
}
}
// Now do reflection, unless we're too deep
if (traceDepth < MAX_DEPTH && MATERIAL_REFLECTION_COEFFICIENT > TINY) {
// Set up the reflected ray - notice we move the origin out a tiny bit again
Vector3f reflectedDir = ray.direction.ReflectIn(surfaceNormal);
Ray reflectionRay = new Ray(ray.hitPoint + reflectedDir * TINY, reflectedDir);
// And trace!
Color reflectionCol = Trace(reflectionRay, traceDepth + 1);
// Add reflection results to running totals, scaling by reflect coeff.
r += MATERIAL_REFLECTION_COEFFICIENT * reflectionCol.R;
g += MATERIAL_REFLECTION_COEFFICIENT * reflectionCol.G;
b += MATERIAL_REFLECTION_COEFFICIENT * reflectionCol.B;
}
// Clamp RGBs
if (r > 255) r = 255;
if (g > 255) g = 255;
if (b > 255) b = 255;
return (Color.FromArgb(255, (int)r, (int)g, (int)b));
}
public override number Intersect(Ray ray) {
number normalDotRayDir = normal.Dot(ray.direction);
if (normalDotRayDir == 0) // Ray is parallel to plane (this early-out won't help very often!)
return -1;
// Any none-parallel ray will hit the plane at some point - the question now is just
// if it in the positive or negative ray direction.
number hitDistance = -(normal.Dot(ray.origin) - distance) / normalDotRayDir;
if (hitDistance < 0) // Ray dir is negative, ie we're behind the ray's origin
return -1;
else
return hitDistance;
}
// Given a ray with origin and direction set, fill in the intersection info
static void CheckIntersection(ref Ray ray) {
foreach (RTObject obj in objects) { // loop through objects, test for intersection
number hitDistance = obj.Intersect(ray); // check for intersection with this object and find distance
if (hitDistance < ray.closestHitDistance && hitDistance > 0) {
ray.closestHitObject = obj; // object hit and closest yet found - store it
ray.closestHitDistance = hitDistance;
}
}
ray.hitPoint = ray.origin + (ray.direction * ray.closestHitDistance); // also store the point of intersection
}
public override number Intersect(Ray ray) {
Vector3f lightFromOrigin = position - ray.origin; // dir from origin to us
number v = lightFromOrigin.Dot(ray.direction); // cos of angle between dirs from origin to us and from origin to where the ray's pointing
number hitDistance =
radius * radius + v * v -
lightFromOrigin.x * lightFromOrigin.x -
lightFromOrigin.y * lightFromOrigin.y -
lightFromOrigin.z * lightFromOrigin.z;
if (hitDistance < 0) // no hit (do this check now before bothering to do the sqrt below)
return -1;
hitDistance = v - (number)Math.Sqrt(hitDistance); // get actual hit distance
if (hitDistance < 0)
return -1;
else
return (number)hitDistance;
}
public abstract number Intersect(Ray ray);
public abstract float Intersect(Ray ray);
// given a ray, trace it into the scene and return the colour of the surface it hits
// (handles bounces recursively)
static Color Trace(Ray ray, int traceDepth)
{
// See if the ray intersected an object (only if it hasn't already got one - we don't need to
// recalculate the first intersection for each sample on the same pixel!)
if (ray.closestHitObject == null)
CheckIntersection(ref ray);
if (ray.closestHitDistance >= Ray.WORLD_MAX || ray.closestHitObject == null) // No intersection
return Color.Black;
// Got a hit - was it an emitter? If so just return the emitter's colour
if (ray.closestHitObject.isEmitter)
return ray.closestHitObject.color;
if (traceDepth >= MAX_DEPTH)
return Color.Black;
// Get surface normal at intersection
Vector3f surfaceNormal = ray.closestHitObject.GetSurfaceNormalAtPoint(ray.hitPoint);
// Pick a point on a hemisphere placed on the intersection point (of which
// the surface normal is the north pole)
if (surfaceNormal.Dot(ray.direction) >= 0)
surfaceNormal = surfaceNormal * -1.0f;
float r1 = (float)(random.NextDouble() * Math.PI * 2.0f);
float r2 = (float)random.NextDouble();
float r2s = (float)Math.Sqrt(r2);
Vector3f u = new Vector3f(1.0f, 0, 0);
if (Math.Abs(surfaceNormal.x) > 0.1f) {
u.x = 0;
u.y = 1.0f;
}
u = Vector3f.CrossProduct(u, surfaceNormal);
u.Normalise();
Vector3f v = Vector3f.CrossProduct(u, surfaceNormal);
// Now set up a direction from the hitpoint to that chosen point
Vector3f reflectionDirection = (u * (float)Math.Cos(r1) * r2s + v * (float)Math.Sin(r1) * r2s + surfaceNormal * (float)Math.Sqrt(1 - r2));
reflectionDirection.Normalise();
// And follow that path (note that we're not spawning a new ray -- just following the one we were
// originally passed for MAX_DEPTH jumps)
Ray reflectionRay = new Ray(ray.hitPoint, reflectionDirection);
Color reflectionCol = Trace(reflectionRay, traceDepth + 1);
// Now factor the colour we got from the reflection
// into this object's own colour; ie, illuminate
// the current object with the results of that reflection
float r = ray.closestHitObject.color.R * reflectionCol.R;
float g = ray.closestHitObject.color.G * reflectionCol.G;
float b = ray.closestHitObject.color.B * reflectionCol.B;
r /= 255.0f;
g /= 255.0f;
b /= 255.0f;
return (Color.FromArgb(255, (int)r, (int)g, (int)b));
}
// render a pixel (ie, set pixel color to result of a trace of a ray starting from eye position and
// passing through the world coords of the pixel)
static Color RenderPixel(int x, int y)
{
// First, calculate direction of the current pixel from eye position
float sx = screenTopLeftPos.x + (x * pixelWidth);
float sy = screenTopLeftPos.y - (y * pixelHeight);
Vector3f eyeToPixelDir = new Vector3f(sx, sy, 0) - eyePos;
eyeToPixelDir.Normalise();
// Set up primary (eye) ray
Ray ray = new Ray(eyePos, eyeToPixelDir);
// And send a bunch of reverse photons that way!
// Since each photon we send into Trace with a depth of 0 will
// bounce around randomly, we need to send many photons into
// every pixel to get good convergence
float r = 0, g = 0, b = 0;
for (int i = 0; i < RAYS_PER_PIXEL; i++) {
Color c = Trace(ray, 1);
r += c.R;
g += c.G;
b += c.B;
}
r /= RAYS_PER_PIXEL;
g /= RAYS_PER_PIXEL;
b /= RAYS_PER_PIXEL;
return (Color.FromArgb(255, (int)r, (int)g, (int)b));
}
