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Controlling image height programatically

  • Hi, Marco!

    Sorry for the late answer!

    That is a good learning example indeed. I will implement this for the Screen Image ( The Image with a Screen Transform Component on it)

    I do this because ScreenTransform has a convenient API that transforms screen point to objects local point. 

    In case if you need to use Image in World Space we can adjust controller later. 


    I decided to modify UV coordinates to achieve desired event. 

    To do this I created a custom Graph Material [add link] 


    I prepared 3 textures:

    1. Contents opacity mask ( black is transparent , white is solid)

    2. Contents itself (with a transparent pixel row at the top)

    3. Glass Image (with transparency)


    Then I pressed Add New -> Graph Unlit , double clicked on created material and set up 

    I am going to change Contents texture UV coordinates to shift it up and down 

    This image has graph scheme. It may seem a bit complicated but it's a nice exercise :

    Double click to see full sized image

    So basically my material has a parameter that can have values from 0 to 1 and affects UМ offset of Contents texture. 

    Let's see how it works 

    Select AddNew -> Screen Image on the Objects panel and assign our material to the image . Then Select GraphMaterial on the Resources and drag the slider to see how it affects Image:


    If you move your cursor over the property of material you can see it's Script Name ( you can also select corresponding node on the material graph editor window)

    Knowing Scripting Name i can modify this property via script. For example : 

    //@input Asset.Material material

    //@input string tweakName = "Tweak_N9"

    script.material.mainPass[script.tweakName] = 0.5;

    Then i made a script that takes a screen position and affects material parameter.

    //@input Component.MaterialMeshVisual image
    //@input Asset.Material material
    //@input string tweakName

    // coefficient for smooth movement
    var smoothKoef = 0.3
    global.touchSystem.touchBlocking = true;
    //creating events
    var touchEndEvent = script.createEvent("TouchEndEvent");
    var touchStartEvent = script.createEvent("TouchStartEvent");
    var touchMoveEvent = script.createEvent("TouchMoveEvent");
    var updateEvent = script.createEvent("UpdateEvent");

    var dragging = false;
    var targetValue = undefined;
    //image has to have screen transform and be a child of a Orthographic camera
    var screenTransform = script.image.getSceneObject().getComponent("Component.ScreenTransform");

    function onTouchStart(eventData) {
    dragging = true;
    targetValue = getValue(eventData.getTouchPosition());
    offset = script.material.mainPass[script.tweakName] - targetValue;
    function onTouchEnd() {
    if (dragging) {
    dragging = false;

    function onTouchMove(eventData) {
    if (dragging) {
    targetValue = getValue(eventData.getTouchPosition());

    function onUpdate() {
    if (targetValue) {
    var currentValue = lerp(script.material.mainPass[script.tweakName], targetValue, smoothKoef);
    script.material.mainPass[script.tweakName] = currentValue;

    function getValue(screenPos) {
    var localPos = screenTransform.screenPointToLocalPoint(screenPos);
    return remap(-1, 1, 0, 1, clamp(-1, 1, localPos.y));

    //helper functions

    function clamp(minValue, maxValue, value) {
    return Math.min(Math.max(minValue, value), maxValue);
    function remap(minFrom, maxFrom, minTo, maxTo, value) {
    return minTo + (maxTo - minTo) * (value - minFrom) / (maxFrom - minFrom);
    function lerp(a, b, t) {
    return a + (b - a) * t

    [Hint] Set Stretch mode of an image to fit height : 

    It's a bit complex but It might give a direction to work on

    Let me know if you have any questions!



    Project file


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