3D テクスチャ
3D テクスチャは、標準の 2 次元ではなく 3 次元の情報を含むビットマップ画像です。3D テクスチャは、フォグや煙などのボリュメトリック効果をシミュレートしたり、ボリュメトリックな 3D メッシュを近似したり、アニメーション化されたテクスチャを格納してそれらを滑らかにブレンドしたりするためによく使用されます。
3D テクスチャサイズ
3D テクスチャの最大解像度は 2048 x 2048 x 2048 です。
Be aware that the size of a 3D texture in memory and on disk increases quickly as its resolution increases. An RGBA32 3D texture with no mipmaps and a resolution of 16 x 16 x 16 has a size of 128KB, but with a resolution of 256 x 256 x 256 it has a size of 512MB.
Importing 3D textures
You can import 3D textures from source texture files that are divided into cells. These are called flipbook textures. To do this:
- Import the source texture into your Unity Project.
- In your Project view, select the resulting Texture Asset. Unity displays the Texture import settings in the Inspector.
- In the Inspector, set Texture Shape to 3D. Unity displays the Columns and Rows properties.
- Set Columns and Rows to the appropriate values for your flipbook texture.
- Click Apply.
For more information, see Texture import settings.
Creating a 3D texture from a script
Unity uses the Texture3D class to represent 3D textures. Use this class to interact with 3D textures in C# scripts.
The following example is an Editor script that creates an instance of the Texture3D class, populates it with color data, and then saves it to your Project as a serialized asset file.
using UnityEditor;
using UnityEngine;
public class ExampleEditorScript : MonoBehaviour
{
[MenuItem("CreateExamples/3DTexture")]
static void CreateTexture3D()
{
// テクスチャを設定
int size = 32;
TextureFormat format = TextureFormat.RGBA32;
TextureWrapMode wrapMode = TextureWrapMode.Clamp;
// テクスチャを作成して設定を適用
Texture3D texture = new Texture3D(size, size, size, format, false);
texture.wrapMode = wrapMode;
// 3D 配列を作成し、カラーデータを保存
Color[] colors = new Color[size * size * size];
// 配列に入力。テクスチャの x, y, z 値が赤、青、緑にマッピングされます。
float inverseResolution = 1.0f / (size - 1.0f);
for (int z = 0; z < size; z++)
{
int zOffset = z * size * size;
for (int y = 0; y < size; y++)
{
int yOffset = y * size;
for (int x = 0; x < size; x++)
{
colors[x + yOffset + zOffset] = new Color(x * inverseResolution,
y * inverseResolution, z * inverseResolution, 1.0f);
}
}
}
// テクスチャにカラー値をコピー
texture.SetPixels(colors);
// Apply the changes to the texture and upload the updated texture to the GPU
texture.Apply();
// テクスチャを Unity プロジェクトに保存
AssetDatabase.CreateAsset(texture, "Assets/Example3DTexture.asset");
}
}
Previewing a 3D texture
The Unity Editor has three different visualization modes you can use to preview a 3D texture:
- Volumetric visualization mode renders the 3D texture as a translucent cube
- Slice visualization mode renders a single slice of each of the three axes of the 3D texture
- SDF visualization mode renders the texture as a Signed Distance Field in 3D space
You can preview the 3D texture in the Inspector, or you can write a script to preview it in the Scene view using the Handles API. Using the Inspector is quick and convenient, but does not allow the use of custom gradients. The Handles API lets you configure the preview to your exact requirements, and allows the use of custom gradients.
Using the Inspector
To preview the 3d texture in the Inspector window:
- In your Project window, select the Texture Asset. The Texture Asset Importer for this Texture Asset is now visible in the Inspector, and Unity renders a preview of the 3D texture at the bottom of the Inspector.
- Navigate to the toolbar above the preview of the 3D texture.
- Use the buttons on the right-hand side of the toolbar to choose between Volumetric, Slice, and SDF visualization modes. The preview image and the buttons on the toolbar change depending on the preview mode.
Volumetric
In this visualization mode, Unity renders the 3D texture as a translucent cube.
ツールバーには以下が用意されています。
| Control: | 機能 |
|---|---|
| Ramp | Enables and disables color ramp visualization. If the image contains a lot of subtle details, enable Ramp to make those details easier to see. |
| Quality | Sets the sample per texture pixel count. Higher values result in a higher quality render. |
| Alpha | Controls the opacity of the visualization. A value of 1 is fully opaque and a value of 0 is fully transparent. Adjust to view the inner pixels. |
Slice
In this visualization mode, Unity renders slices of each axis plane of the 3D texture.
ツールバーには以下が用意されています。
| Control: | 機能 |
|---|---|
| Ramp | Enables and disables color ramp visualization. If the image contains a lot of subtle details, enable Ramp to make those details easier to see. |
| X | Sets the slicing position on the x axis, in texture pixels. Adjust to view a specific slice. |
| Y | Sets the slicing position on the y axis, in texture pixels. Adjust to view a specific slice. |
| Z | Sets the slicing position on the z axis, in texture pixels. Adjust to view a specific slice. |
SDF
In this visualization mode, Unity uses Signed Distance Field rendering mode in 3D space to render the 3D texture. Note that this visualization mode supports only non-directional Signed Distance Fields.
ツールバーには以下が用意されています。
| Control: | 機能 |
|---|---|
| Scale | The number by which to multiply the ray step size. The ray step size is the distance between 2 neighboring pixels. If distant parts of the visualization are cut off, try increasing this. If the visualization is not rendered at all, try decreasing this. |
| Offset | The intensity of the pixels at which the surface is rendered. When this value is positive, Unity will expand the rendered surface. When this value is negative, Unity will render empty space as a surface, and a surface as empty space. |
Using the Handles API
For information on previewing a 3D texture using the Handles API and code samples, see the following documentation:
シェーダーで 3D テクスチャを使用
以下は、3D テクスチャを使用してボリュームを視覚化する簡単なレイマーチングシェーダーの例です。
Shader "Unlit/VolumeShader"
{
Properties
{
_MainTex ("Texture", 3D) = "white" {}
_Alpha ("Alpha", float) = 0.02
_StepSize ("Step Size", float) = 0.01
}
SubShader
{
Tags { "Queue" = "Transparent" "RenderType" = "Transparent" }
Blend One OneMinusSrcAlpha
LOD 100
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
//レイマーチングサンプルの最大数
#define MAX_STEP_COUNT 128
// 可能な浮動小数点の不正確性
#define EPSILON 0.00001f
struct appdata
{
float4 vertex : POSITION;
};
struct v2f
{
float4 vertex : SV_POSITION;
float3 objectVertex : TEXCOORD0;
float3 vectorToSurface : TEXCOORD1;
};
sampler3D _MainTex;
float4 _MainTex_ST;
float _Alpha;
float _StepSize;
v2f vert (appdata v)
{
v2f o;
// オブジェクト空間の頂点。これがレイマーチングの開始点になります
o.objectVertex = v.vertex;
// ワールド空間でカメラから頂点までのベクトルを計算します
float3 worldVertex = mul(unity_ObjectToWorld, v.vertex).xyz;
o.vectorToSurface = worldVertex - _WorldSpaceCameraPos;
o.vertex = UnityObjectToClipPos(v.vertex);
return o;
}
float4 BlendUnder(float4 color, float4 newColor)
{
color.rgb += (1.0 - color.a) * newColor.a * newColor.rgb;
color.a += (1.0 - color.a) * newColor.a;
return color;
}
fixed4 frag(v2f i) : SV_Target
{
// オブジェクトの前面でレイマーチングを開始します
float3 rayOrigin = i.objectVertex;
// カメラからオブジェクトサーフェスへのベクトルを使用してレイの方向を取得
float3 rayDirection = mul(unity_WorldToObject, float4(normalize(i.vectorToSurface), 1));
float4 color = float4(0, 0, 0, 0);
float3 samplePosition = rayOrigin;
// オブジェクト全体にレイマーチ
for (int i = 0; i < MAX_STEP_COUNT; i++)
{
// 単位立方体の範囲内でのみ色を累積します
if(max(abs(samplePosition.x), max(abs(samplePosition.y), abs(samplePosition.z))) < 0.5f + EPSILON)
{
float4 sampledColor = tex3D(_MainTex, samplePosition + float3(0.5f, 0.5f, 0.5f));
sampledColor.a *= _Alpha;
color = BlendUnder(color, sampledColor);
samplePosition += rayDirection * _StepSize;
}
}
return color;
}
ENDCG
}
}
}
ページ上の例で作成した 3D テクスチャでこのシェーダーを使用すると、 結果は以下のようになります。
