Generate a dynamic animation showcasing transparency effects, uncovering the intricate Mesh structure within threejs

Question

Generate a dynamic animation showcasing transparency effects, uncovering the intricate Mesh structure within threejs

Is there a way to achieve a linear animation in THREE.JS that reveals a complex 3D mesh from the bottom to the top, similar to a slideUp effect in 2D jQuery objects?

After searching for options such as opacity channels or maps, it seems that they are not possible solutions for this task.

Using sprites of textures and adjusting offsets may not be ideal due to the complexity of my UV map.

Are there any methods available in THREE.JS that can help create this desired effect?

javascript three.js webgl

Answer 1

Answer №1

Transform the complete scene into the first framebuffer (texture).
Transform only the mesh into the second framebuffer (texture).

Display a fullscreen rectangle that utilizes the two textures mentioned earlier, using a variation of the following code:

uniform sampler2D texScene;
uniform sampler2D texMesh;

uniform vec2 uResolution;
uniform float time;

void main() {
    vec2 uv = gl_FragCoord.xy / uResolution;

    vec3 s = texture2D( texScene, uv ).xyz;
    vec4 m = texture2D( texMesh, uv );

    // slide up effect
    float percent = clamp( time, 0, endAnim ) / endAnim;  // endAnim is the time animation ends (assuming animation starts at time=0)

    vec3 color = s;
    if( uv.y > (1.0 - percent) ) {
        color = s * (1.0 - m.a) + m.xyz * m.a;
    }
    gl_FragColor = vec4( color, 1.0 );
}

The functioning of the code should be easily understood. Based on the passed time, it determines the current stage of the animation and decides whether to incorporate the mesh's color or display only the background color.

I trust this explanation is useful.

Answer 2

Transform the complete scene into the first framebuffer (texture).
Transform only the mesh into the second framebuffer (texture).

Display a fullscreen rectangle that utilizes the two textures mentioned earlier, using a variation of the following code:

uniform sampler2D texScene;
uniform sampler2D texMesh;

uniform vec2 uResolution;
uniform float time;

void main() {
    vec2 uv = gl_FragCoord.xy / uResolution;

    vec3 s = texture2D( texScene, uv ).xyz;
    vec4 m = texture2D( texMesh, uv );

    // slide up effect
    float percent = clamp( time, 0, endAnim ) / endAnim;  // endAnim is the time animation ends (assuming animation starts at time=0)

    vec3 color = s;
    if( uv.y > (1.0 - percent) ) {
        color = s * (1.0 - m.a) + m.xyz * m.a;
    }
    gl_FragColor = vec4( color, 1.0 );
}

The functioning of the code should be easily understood. Based on the passed time, it determines the current stage of the animation and decides whether to incorporate the mesh's color or display only the background color.

I trust this explanation is useful.

Answer 3

Answer №2

Another option is to render the building on the screen by using the code

gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)

and creating an alpha gradient for the building (from top to bottom).

When drawing to any output, WebGL considers the source information and the destination information (what has already been drawn to the output) and combines them according to your instructions.

The process of drawing to an output can be summarized as follows:

SOURCE_VALUE * [SOURCE_FACTOR] [BLEND EQUATION] DESTINATION_VALUE * [DESTINATION_FACTOR];

The default equation is:

SOURCE_VALUE * 1 + DESTINATION_VALUE * 0;

This equation essentially replaces all existing information in the buffer with the new information. What we aim to achieve is to retain the existing information where we are not drawing and only incorporate the new information where we are drawing. This modifies the equation to:

SOURCE_VALUE * SRC_ALPHA + DESTINATION_VALUE * ONE_MINUS_SRC_ALPHA;

If one fragment of your building is 20% transparent, it will display 20% of the building's color and 80% of the color of what lies behind the building.

This method of rendering semitransparent objects takes into account the depth buffer.

Answer 4

Another option is to render the building on the screen by using the code

gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)

and creating an alpha gradient for the building (from top to bottom).

When drawing to any output, WebGL considers the source information and the destination information (what has already been drawn to the output) and combines them according to your instructions.

The process of drawing to an output can be summarized as follows:

SOURCE_VALUE * [SOURCE_FACTOR] [BLEND EQUATION] DESTINATION_VALUE * [DESTINATION_FACTOR];

The default equation is:

SOURCE_VALUE * 1 + DESTINATION_VALUE * 0;

This equation essentially replaces all existing information in the buffer with the new information. What we aim to achieve is to retain the existing information where we are not drawing and only incorporate the new information where we are drawing. This modifies the equation to:

SOURCE_VALUE * SRC_ALPHA + DESTINATION_VALUE * ONE_MINUS_SRC_ALPHA;

If one fragment of your building is 20% transparent, it will display 20% of the building's color and 80% of the color of what lies behind the building.

This method of rendering semitransparent objects takes into account the depth buffer.

Answer 5

Answer №3

I came up with a different approach.

Instead of using multiple textures with repeated patterns for the building, I decided to use one texture for the entire structure. I arranged the UVs vertically in a progressive manner, aligning the faces from bottom to top on the texture. To add animation, I utilized a canvas texture and filled it with a transparent rectangle.

// x - current step
// steps - number of steps

var canvas = document.getElementById('canvas-texture'),
    ctx    = canvas.getContext('2d');

ctx.beginPath();
ctx.drawImage(image, 0, 0);
ctx.globalCompositeOperation = 'destination-out';
ctx.fillRect(0, 0, width, height/steps * x);
ctx.closePath();

Since I needed a solution quickly, I plan to experiment with your suggestions over the weekend. I can also create a demo showcasing my approach if you're interested.

Thanks to everyone for your assistance.

Answer 6

I came up with a different approach.

Instead of using multiple textures with repeated patterns for the building, I decided to use one texture for the entire structure. I arranged the UVs vertically in a progressive manner, aligning the faces from bottom to top on the texture. To add animation, I utilized a canvas texture and filled it with a transparent rectangle.

// x - current step
// steps - number of steps

var canvas = document.getElementById('canvas-texture'),
    ctx    = canvas.getContext('2d');

ctx.beginPath();
ctx.drawImage(image, 0, 0);
ctx.globalCompositeOperation = 'destination-out';
ctx.fillRect(0, 0, width, height/steps * x);
ctx.closePath();

Since I needed a solution quickly, I plan to experiment with your suggestions over the weekend. I can also create a demo showcasing my approach if you're interested.

Thanks to everyone for your assistance.

Generate a dynamic animation showcasing transparency effects, uncovering the intricate Mesh structure within threejs

Answer №1

Answer №2

Answer №3

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