Question

i have a texture applied to a plane, and would like on screen touch to erase the selected location on that plane (like an eraser) so that in the location i have touched, the texture should be transparent. How can i do so?

Answer 1

Following your clarification in the comments above will this work:

Texture2D texture = renderer.material.mainTexture;
Color color = new Color(0.5F, 0.5f, 0.5F, 0.5F);  //example color, grey w/ half opacity

texture.SetPixel(0,0,color); //set pixel (0,0) to the color specified
texture.Apply();  //Must be called at least once after all changes to pixels made

Hopefully that’s what you need. Obviously you’ll need to add the code to modify only pixels near to where your cursor hits.