Real-Time Rendering Techniques

# Real-Time Rendering Techniques

Real-time rendering (RTR) is the process of generating an image from a model by means of computer programs. It involves a balance between achieving high-quality visuals and maintaining a high frame rate. Let's cover some key techniques used in RTR.

## 1. Rasterization

Rasterization is a process that converts geometric data into a raster format (grid of pixels). It is widely used due to its speed, which makes it suitable for real-time rendering.

```cpp
void rasterizeTriangle(Triangle tri, Image img) {
  for (int y = 0; y < img.height; y++) {
    for (int x = 0; x < img.width; x++) {
      if (isInsideTriangle(x, y, tri)) {
        img.setPixel(x, y, tri.color);
      }
    }
  }
}
```

## 2. Ray Tracing

Ray tracing simulates the physical behavior of light to generate high-quality, photorealistic images. Despite its computational cost, recent advances in GPU technology have begun to enable its use in real-time applications.

```cpp
Color rayTrace(Ray ray, Scene scene) {
  Intersection closest = findClosestIntersection(ray, scene);
  if (closest.exists) {
    return calculateLighting(closest, scene);
  } else {
    return scene.backgroundColor;
  }
}
```

## 3. Shading Languages

Shading languages like GLSL or HLSL allow developers to program shaders, which control the final pixel color in a rendering. Shaders play a crucial role in achieving various effects (e.g., shadowing, reflections) in real-time rendering.

```glsl
#version 330 core
out vec4 FragColor;
in vec3 ourColor;
void main()
{
    FragColor = vec4(ourColor, 1.0);
}
```

## 4. Physically-Based Rendering (PBR)

PBR is a shading model that simulates the interaction between light and materials in a physically accurate manner. It's commonly used in modern game engines to achieve realistic visuals.

```glsl
vec3 fresnelSchlick(float cosTheta, vec3 F0)
{
    return F0 + (1.0 - F0) * pow(1.0 - cosTheta, 5.0);
}
```

Remember, these techniques often work together. For example, rasterization might be used to render geometry, while ray tracing is used for lighting and shadows. This combination allows for high-quality visuals at a performance suitable for real-time applications.