Why shaders control visual rendering in Unity - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a shader property for color.

Unity

Shader "Custom/SimpleColor" {
  Properties {
    _Color ("Color", Color) = [1]
  }
}

Drag options to blanks, or click blank then click option'

A(1,1,1,1)

Bred

Cfloat4(1,0,0,1)

D"blue"

Attempts:

3 left

💡 Hint

Common Mistakes

Using color names as strings instead of numeric vectors.

Using incorrect syntax like float4 without proper context.

Shader color properties use a vector with four float values representing RGBA, like (1,1,1,1) for white.

2fill in blank

medium

Complete the code to sample the main texture in the fragment shader.

Unity

fixed4 frag(v2f i) : SV_Target {
  fixed4 col = tex2D([1], i.uv);
  return col;
}

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Auv

Bsampler2D

Cfloat4

D_MainTex

Attempts:

3 left

💡 Hint

Common Mistakes

Using the type name instead of the sampler variable.

Passing UV coordinates incorrectly.

The tex2D function samples a texture using its sampler variable, usually named _MainTex.

3fill in blank

hard

Fix the error in the shader code to correctly multiply color by light intensity.

Unity

fixed4 frag(v2f i) : SV_Target {
  fixed4 col = tex2D(_MainTex, i.uv);
  fixed light = [1].r;
  return col * light;
}

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AlightIntensity

BlightDir

ClightColor

DlightPos

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names that don't exist or hold different data.

Multiplying by a vector instead of a scalar.

The light color variable holds intensity information; multiplying color by lightColor.r applies lighting.

4fill in blank

hard

Fill both blanks to declare and use a float property controlling brightness.

Unity

Properties {
  _Brightness ("Brightness", Float) = [1]
}

fixed4 frag(v2f i) : SV_Target {
  fixed4 col = tex2D(_MainTex, i.uv);
  col.rgb *= [2];
  return col;
}

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A1.0

B0.5

C_Brightness

D_Color

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong property name in the shader code.

Setting default value as a string instead of a number.

The brightness property is declared with a default value 1.0 and used in the shader as _Brightness to scale color.

5fill in blank

hard

Fill all three blanks to create a simple vertex shader that moves vertices up by a float amount.

Unity

Shader "Custom/MoveUp" {
  Properties {
    _MoveAmount ("Move Amount", Float) = [1]
  }
  SubShader {
    Pass {
      CGPROGRAM
      #pragma vertex vert
      #pragma fragment frag

      float [2];

      struct appdata {
        float4 vertex : POSITION;
      };

      struct v2f {
        float4 pos : SV_POSITION;
      };

      v2f vert(appdata v) {
        v2f o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.pos.y += [3];
        return o;
      }

      fixed4 frag(v2f i) : SV_Target {
        return fixed4(1,1,1,1);
      }
      ENDCG
    }
  }
}

Drag options to blanks, or click blank then click option'

A0.5

B_MoveAmount

Cv.vertex.y

DmoveAmount

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than the property name.

Trying to add vertex.y directly instead of the property.

The float property _MoveAmount is declared with default 0.5, then used as variable _MoveAmount to add to vertex y position.

Practice

1. What is the main role of a shader in Unity's visual rendering?

easy

A. To decide how an object looks by controlling its color and lighting

B. To move objects around in the game world

C. To handle user input like keyboard and mouse

D. To save game data to the disk

Solution

1. Step 1: Understand what shaders do

   Shaders control the appearance of objects by defining their color, texture, and lighting effects.

2. Step 2: Compare with other options

   Moving objects, handling input, and saving data are not tasks of shaders but of other systems.

3. Final Answer:

   To decide how an object looks by controlling its color and lighting -> Option A

4. Quick Check:

   Shaders control appearance = B [OK]

Hint: Shaders control look and light, not movement or input [OK]

Common Mistakes:

• Confusing shaders with scripts that move objects
• Thinking shaders handle input or data saving
• Believing shaders only add textures without lighting

2. Which of the following is the correct way to declare a simple color property in a Unity shader?

easy

A. color _Color = (1, 0, 0, 1); // Red color

B. float4 _Color = float4(1, 0, 0, 1); // Red color

C. float _Color = (1, 0, 0, 1); // Red color

D. vec4 _Color = vec4(1, 0, 0, 1); // Red color

Solution

1. Step 1: Identify Unity shader syntax for color

   Unity shaders use HLSL syntax where colors are declared as float4 variables.

2. Step 2: Check each option

   float4 _Color = float4(1, 0, 0, 1); // Red color uses float4 correctly. color _Color = (1, 0, 0, 1); // Red color uses 'color' which is invalid. float _Color = (1, 0, 0, 1); // Red color uses float for a vector, which is wrong. vec4 _Color = vec4(1, 0, 0, 1); // Red color uses 'vec4' which is GLSL, not Unity HLSL.

3. Final Answer:

   float4 _Color = float4(1, 0, 0, 1); // Red color -> Option B

4. Quick Check:

   Unity shader colors use float4 = A [OK]

Hint: Use float4 for colors in Unity shaders, not vec4 or color [OK]

Common Mistakes:

• Using GLSL syntax like vec4 instead of HLSL float4
• Declaring color as a single float instead of a vector
• Using undefined types like 'color'

3. Given this simple shader snippet in Unity:

fixed4 frag(v2f i) : SV_Target {
    return fixed4(0, 1, 0, 1);
}

What color will the object appear?

medium

A. Green

B. Red

C. Blue

D. Transparent

Solution

1. Step 1: Analyze the return color values

   The function returns fixed4(0, 1, 0, 1) which means red=0, green=1, blue=0, alpha=1.

2. Step 2: Determine the visible color

   Since green is 1 and others are 0, the object will appear green and fully opaque.

3. Final Answer:

   Green -> Option A

4. Quick Check:

   fixed4(0,1,0,1) = Green [OK]

Hint: RGBA order: fixed4(0,1,0,1) means green [OK]

Common Mistakes:

• Mixing up RGB order
• Thinking alpha=1 means transparent
• Assuming fixed4 values are percentages

4. This shader code snippet has an error:

fixed4 frag(v2f i) : SV_Target {
    fixed4 color = fixed4(1, 0, 0);
    return color;
}

What is the error?

medium

A. Using fixed4 instead of float4

B. Incorrect return type for frag function

C. Variable 'color' is not declared

D. Missing alpha value in fixed4 constructor

Solution

1. Step 1: Check fixed4 constructor parameters

   fixed4 requires 4 values (red, green, blue, alpha). The code provides only 3.

2. Step 2: Identify the missing value

   The alpha (opacity) value is missing, causing a syntax error.

3. Final Answer:

   Missing alpha value in fixed4 constructor -> Option D

4. Quick Check:

   fixed4 needs 4 values = D [OK]

Hint: fixed4 needs 4 values: R, G, B, and alpha [OK]

Common Mistakes:

• Forgetting alpha in color vectors
• Confusing fixed4 with float4 (both valid but context matters)
• Assuming 3 values are enough for fixed4

5. You want to create a shader that changes an object's color based on its height (Y position). Which shader feature controls this visual effect?

hard

A. Using audio input to modify color dynamically

B. Using physics engine to detect height and change color

C. Using vertex shader to pass height data and fragment shader to color accordingly

D. Using camera settings to adjust color based on distance

Solution

1. Step 1: Understand how shaders use data

   Vertex shaders process vertex positions, so they can pass height info to fragment shaders.

2. Step 2: Apply height to color in fragment shader

   The fragment shader uses the height data to decide the color output, creating the effect.

3. Step 3: Eliminate other options

   Physics, audio, and camera settings do not directly control shader color based on height.

4. Final Answer:

   Using vertex shader to pass height data and fragment shader to color accordingly -> Option C

5. Quick Check:

   Vertex + fragment shaders control visual effects = C [OK]

Hint: Use vertex shader for position, fragment shader for color [OK]

Common Mistakes:

• Thinking physics or audio control shader colors
• Confusing camera effects with shader color control
• Not using vertex data to influence fragment color