Hello everyone, I am Teacher Xiao Yu! Today, I will lead you to explore a very interesting topic – the application of C language in graphics. As a programmer, being able to create stunning 3D worlds with code is a really cool thing! We will start with the basic principles of ray tracing and gradually master the methods of building 3D graphics.
1. Basics of Ray Tracing
1.1 What is Ray Tracing?
Ray Tracing is an algorithm that simulates the propagation of light rays. Imagine when we take a photo with a camera, light reflects off objects and forms an image on the lens. Ray tracing simulates this process in reverse – it emits rays from the observer’s perspective and calculates their intersection points with objects in the scene.
Here’s a simple example of ray tracing code:
typedef struct { float x, y, z; // 3D vector} Vector3;
typedef struct { Vector3 origin; // Ray origin Vector3 direction; // Ray direction} Ray;
// Calculate intersection of ray with sphere
bool intersectSphere(Ray ray, Vector3 center, float radius, float* t) { Vector3 oc = { // Vector from ray origin to sphere center ray.origin.x - center.x, ray.origin.y - center.y, ray.origin.z - center.z };
// Solve quadratic equation float a = dot(ray.direction, ray.direction); float b = 2.0f * dot(oc, ray.direction); float c = dot(oc, oc) - radius * radius; float discriminant = b*b - 4*a*c;
if (discriminant < 0) return false; *t = (-b - sqrt(discriminant)) / (2.0f*a); return *t >= 0;}1.2 Basic Lighting Models
In 3D rendering, we need to consider three basic types of lighting:
•Ambient Light: Basic brightness from all directions•Diffuse Light: Scattering of light on the object’s surface•Specular Light: Creates highlight effects
2. Basics of 3D Modeling
2.1 Mesh Models
Mesh is the most common representation of 3D models, composed of vertices and faces. Imagine origami, where we piece together multiple triangles to form a solid shape:
typedef struct { Vector3* vertices; // Vertex array int* indices; // Vertex indices int vertexCount; int indexCount;} Mesh;
// Create a simple cube
Mesh createCube() { Mesh cube; // 8 vertices cube.vertexCount = 8; cube.vertices = malloc(sizeof(Vector3) * 8); // Set vertex coordinates // ... (specific coordinate settings omitted)
// 12 triangles (6 faces) cube.indexCount = 36; // 12 * 3 cube.indices = malloc(sizeof(int) * 36); // Set indices return cube;}2.2 Transformation Matrices
To achieve rotation, scaling, and translation of objects, we need to use transformation matrices. It’s like giving an object a “movement instruction”:
typedef struct { float m[4][4]; // 4x4 matrix} Matrix4;
// Create translation matrix
Matrix4 createTranslationMatrix(float x, float y, float z) { Matrix4 m = {0}; // Initialize to 0 m.m[0][0] = 1.0f; m.m[1][1] = 1.0f; m.m[2][2] = 1.0f; m.m[3][3] = 1.0f; m.m[3][0] = x; m.m[3][1] = y; m.m[3][2] = z; return m;}3. Practical Exercise
Let’s do a little exercise! Try to implement a simple scene rendering:
1.Create a sphere and a plane2.Add a point light source3.Implement basic lighting calculations4.Render to PPM format image
Tip: You can start with the simplest case and gradually add features.
Summary
Today we learned:
•Basic principles of ray tracing•Representation of 3D mesh models•Basic transformation matrices•Simple rendering implementation
Remember, graphics is a field that requires a lot of practice. I recommend starting with simple shapes and gradually adding more features. Next time, we will delve into material systems and more advanced rendering techniques!
Exercises:
1.Try modifying the sphere intersection calculation code to handle multiple spheres2.Implement a simple camera system3.Add simple shadow effects to the rendering results
Learning Tips:
•Draw the relationship between light rays and objects on paper•Practice starting from 2D scenes•Use visualization tools to aid understanding•Check the code of open-source renderers
Happy coding everyone! If you have any questions, feel free to ask me! 😊