Terrain system basics in Unity - Step-by-Step Execution

Concept Flow - Terrain system basics

Start Unity Project

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Create Terrain Object

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Set Terrain Size & Resolution

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Modify Terrain Height

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Apply Textures & Details

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Add Trees & Objects

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Test & Adjust Terrain

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Save Scene & Project

This flow shows the basic steps to create and customize a terrain in Unity, from starting a project to saving the final terrain.

Execution Sample

Unity

Terrain terrain = Terrain.CreateTerrainGameObject(new TerrainData()).GetComponent<Terrain>();
terrain.terrainData.size = new Vector3(500, 100, 500);
float[,] heights = new float[513, 513];
heights[256, 256] = 0.5f;
terrain.terrainData.SetHeights(0, 0, heights);

This code creates a terrain, sets its size, modifies the height at the center, and applies the height changes.

Execution Table

Step	Action	Variable/Property Changed	Value After Action	Notes
1	Create Terrain GameObject	terrain	Terrain object created	Terrain object is ready to use
2	Set terrain size	terrain.terrainData.size	(500, 100, 500)	Terrain dimensions set (width, height, length)
3	Create heights array	heights	513x513 float array initialized with 0	All heights start flat at 0
4	Set center height	heights[256,256]	0.5	Raise center point to half max height
5	Apply heights to terrain	terrain.terrainData.SetHeights	Heights updated	Terrain surface updated with new heights

💡 All steps complete, terrain created and modified successfully

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
terrain	null	Terrain object created	Terrain object created	Terrain object created
terrain.terrainData.size	(1000, 600, 1000) default	(500, 100, 500)	(500, 100, 500)	(500, 100, 500)
heights	null	513x513 array of 0	513x513 array with center 0.5	513x513 array with center 0.5

Key Moments - 3 Insights

Why do we use a 2D array for heights?

Because the terrain surface is a grid of points, each with a height value, so a 2D array matches the terrain layout (see Step 3 and 4 in execution_table).

What does setting terrain.terrainData.size do?

It changes the physical size of the terrain in the world (width, height, length), not just the height values (see Step 2).

Why do we call SetHeights after changing the array?

Because modifying the array alone doesn't update the terrain; SetHeights applies the changes to the terrain surface (see Step 5).

Visual Quiz - 3 Questions

Look at the execution table, what is the height value at the center point after Step 4?

A 1.0

B 0

C 0.5

D Undefined

💡 Hint

Check the 'Value After Action' column for Step 4 in the execution_table.

At which step is the terrain size changed?

A Step 2

B Step 1

C Step 4

D Step 5

💡 Hint

Look for 'Set terrain size' in the Action column of execution_table.

If we skip calling SetHeights, what happens to the terrain?

A Terrain height changes are visible

B Terrain remains flat

C Terrain size changes

D Terrain is deleted

💡 Hint

Refer to Step 5 notes in execution_table about applying height changes.

Concept Snapshot

Unity Terrain Basics:
- Create terrain with Terrain.CreateTerrainGameObject()
- Set size via terrain.terrainData.size
- Modify heights using a 2D float array
- Apply heights with terrain.terrainData.SetHeights(x, y, heights)
- Changes update the visible terrain surface

Full Transcript

This visual execution shows how to create and modify a terrain in Unity. First, a terrain object is created. Then, its size is set to control the physical dimensions. A 2D array of floats represents the height map, where each value controls the height at a grid point. We modify the center height to raise it. Finally, we apply these heights to the terrain using SetHeights, which updates the visible terrain surface. This step-by-step trace helps beginners see how terrain data changes affect the final terrain.