Determine Position of Light Relative to a Tile in a Godot Shader: A Comprehensive Guide

For this tutorial, we’ll use a simple grid-based tilemap with a single light source. You can adjust the tilemap and light settings to fit your specific needs.

The Shader Code

Now that we have our project set up, let’s create a new shader material in Godot. Create a new file called `light Relative.shader` and add the following code:

shader_type canvas_item;

uniform vec2 lightPosition : hint_distance;
uniform vec2 tileSize : hint_distance;

void fragment() {
    vec2 texCoord = UV * tileSize;
    vec2 lightDir = lightPosition - texCoord;
    float dist = length(lightDir);
    float angle = atan(lightDir.y, lightDir.x);
    COLOR = vec4(angle, dist, 0, 1);
}

Let’s break down this code step by step:

• uniform vec2 lightPosition : hint_distance;: We define a uniform variable lightPosition to store the position of the light source in 2D space. The hint_distance hint tells Godot to treat this variable as a distance value.
• uniform vec2 tileSize : hint_distance;: We define another uniform variable tileSize to store the size of each tile in the tilemap. Again, we use the hint_distance hint to indicate that this variable represents a distance value.
• vec2 texCoord = UV * tileSize;: We calculate the texture coordinates texCoord by multiplying the UV coordinates with the tileSize. This gives us the position of the current tile in 2D space.
• vec2 lightDir = lightPosition - texCoord;: We calculate the direction vector lightDir from the light source to the current tile by subtracting the tile position from the light position.
• float dist = length(lightDir);: We calculate the distance dist from the light source to the current tile by taking the length of the lightDir vector.
• float angle = atan(lightDir.y, lightDir.x);: We calculate the angle angle of the light direction using the atan function, which takes the y and x components of the lightDir vector as arguments.
• COLOR = vec4(angle, dist, 0, 1);: Finally, we set the output color COLOR to a vec4 value containing the calculated angle, distance, and alpha values.

Explaining the Magic

The shader code above is where the magic happens. By subtracting the tile position from the light position, we effectively calculate the direction vector from the light source to the current tile. This direction vector is then used to calculate the distance and angle of the light direction, which are essential for determining the position of light relative to the tile.

The atan function is used to calculate the angle of the light direction, which is then stored in the angle variable. This angle value will be used to determine the position of light relative to the tile.

Using the Shader in Godot

Now that we have the shader code, let’s apply it to our tilemap in Godot. Create a new material and assign the `lightRelative.shader` file to it.

Next, create a new `ShaderMaterial` node and add it to your scene. Assign the material we just created to the `ShaderMaterial` node.

In the `ShaderMaterial` node, add two uniform variables: `lightPosition` and `tileSize`. Set the `lightPosition` variable to the position of your light source, and set the `tileSize` variable to the size of your tilemap tiles.

Visualizing the Results

Now that we have our shader set up, let’s visualize the results. Create a new `Sprite` node and add it to your scene. Assign the `ShaderMaterial` node to the `Sprite` node.

In the `Sprite` node, set the `texture` property to a noise texture or any other texture that will help you visualize the lighting effect.

Run the scene and observe the output. You should see a beautiful, gradient-like effect that indicates the position of light relative to each tile. The angle and distance values calculated in the shader will give you an accurate representation of the light direction and intensity.

Tweaking and Optimizing

Now that we have a working shader, let’s tweak and optimize it to achieve the desired visual effects.

You can adjust the shader code to use different formulas for calculating the angle and distance values. Experiment with different math functions, such as `sin` and `cos`, to create unique lighting effects.

Additionally, you can optimize the shader code by reducing the number of calculations or using texture sampling to improve performance.

Conclusion

In this comprehensive guide, we’ve explored the techniques for determining the position of light relative to a tile in a Godot shader. By using a simple shader code and tweaking it to fit your specific needs, you can create stunning lighting effects that will elevate your game development to the next level.

Remember to experiment with different shader techniques and formulas to achieve unique visual effects. And don’t forget to optimize your shader code for performance to ensure a smooth gaming experience.

Happy coding, and see you in the next tutorial!

Further Reading

For more information on Godot shader programming, check out the official Godot documentation and the following resources:

• Godot Shader Tutorial
• Shader Forge
• Godot Demo Reels – Shaders

Frequently Asked Question

Get ready to shine a light on your Godot game development with these FAQs about determining the position of light relative to a tile in a Godot shader!