I have two textures which one is above the other. When user drags finger on the screen I get the path of the finger and I can draw any colour I want above the two textures following the finger path and drawing GL Triangles.
However, rather than drawing I want to change the alpha value of the above texture to 0 where the finger path is, so the below texture will be shown (where the finger path is). Is this possible to be done with Libgdx because I can't find how. If not, do you have any other suggestions how can this be implemented?
This is more or less how a paint eraser would work.
Thanks
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I want to draw some path with user's touch. if users moves finger from one position to another position a path will be drawn exactly as user moved finger.
We can draw a line with by defining color but i want to draw that line with sprite(image).
What I exactly meant is I just want to use image using sprite instead of using color to draw line. is it possible with LibGDX? if yes , how can we do that? and how will I generate image to use as sprite for that?
I'm struggling with something I would expect to be straight forward with libgdx.
In short this is a "finger paint" app where I want to draw a path of a certain width where the user touches the screen.
I've earlier done this by using a plain Android android.view.View. I had a android.graphics.Path in which I stored the coordinates of the user's current touch. In the onDraw() method of the view I drew the path to the android.graphics.Canvas. Whenever the user released a finger I drew the path to an offline canvas/android.graphics.Bitmap which also was drawn in the onDraw() method. Plain and simple.
How can that be done using libgdx?
I have tried using a com.badlogic.gdx.graphics.Pixmap that I can draw a line to whenever the user moves a finger. This works well except the fact that I'm unable to control the witdh of the line using Gdx.gl.glLineWidth(). I know I can draw a rectangle instead of a line to set the width, but Pixmap doesn't seem to have any means of rotating, so I don't see how this can be done.
I can use a com.badlogic.gdx.graphics.glutils.ShapeRenderer for drawing lines (or rectangles) in com.badlogic.gdx.Screen.render(). As far as I can see I then need to store every single touch point of the current touch, and then draw all lines on render. Whenever the user relases a finger I guess I can store the screen as-is with something like com.badlogic.gdx.utils.ScreenUtils.getFrameBufferPixmap(). Hopefully there is a easier way to achieve what I want.
I ended up drawing circles on a pixmap where the line should be:
One circle on touchDown
Several circles from last touch point to next touch point reported to touchDragged
I'm not very happy with this solution, but it kinda works.
Maybe you can calculate line dot coordinates manually and use triangles to draw them on pixmap? Like use 2 triangles to form (rotated) box?
I have a 3d mesh, which is a terrain. This runs perfectly fine btw, but I want to have shapes moving accross this terrain. These shapes are flat on the landscape and are blob-like: They can change shape and should follow the contoures and the heightmap of the terrain. These shapes can be painted on the landscape or flow over it, that doesn't matter.
The shapes are meant to be blocks of armies moving across the map, and this should be happening Real-Time! Also: they are 2d convex hull shapes. Also they are just one color with an alpha value (like blue with alpha 0.25f).
The only problem is: I can't figure out how to do this and the question is: Can anyone tell me how to do it?
My first thoughts were just to copy the terrain vertex matrix, push it up a bit so it will be on top of the terrain, load this buffer into a VBO and update the index buffer according to the position and shape needed and then draw the shape. This is rather slow and inefficient, especially when the shape is moving and changing. Also, the resolution of the heightmap is 175x175, so the movement is not at all smooth but rather jaggy.
Then I thought, but rather new to this area, update the shape outlines to the fragment shader of the terrain and let the shader decide if a point lies in that area and change color accordingly. This also was a really slow option, but if anyone sees potential and a good way to do this, tell me!
The next option was to draw directly onto the texture, which is still in the failing stage. If someone has any good ideas on how to draw a scene to a flat area and then put that on a terrain mesh, that would be great!
So if anyone has a solution to draw a shape (or multiple) on a terrain? That would be awesome. Thanks in advance!
I load an STL mesh, draw it correctly (using GL_TRIANGLES), rotate nicely, change colour, the lights stay in position while the mesh moves, everything is great. Then I switch off the triangles and display just the vertices (using GL_POINTS), now when I rotate (and even when I display the triangles and the vertices together) the points seem to fade out as I rotate - as if they are lit from only one side.
Does this ring any bells with anyone?
Thanks for any help.
Baz
It maybe just a perception artefact. If you still got lighting on, the points are of course lit like the triangle vertices (depending on their normals), meaning they actually have an orientation, even if this is not intuitive for points. So they may get darker or brighter when rotating them into/away from the light. It's just that this change seems more evident, because you don't have the other surface points to fill the gaps and compensate for the dimming. Try disabling lighting and they should keep their color when rotating.
I'm new to opengl-es on android and struggling to get my head around the concept of texturing.
I am looking to produce a tilemap of various difference textures. I understand that it is better to use an atlas of all the combined textures so I don't repeatedly rebind. However I am unsure quite how to then map these textures on to my tilemap.
I understand the process of specifiying vertices and then coordinates of where on the texture map I wish to take them from (i drew a picture too!)
Click for image - curse newbies not allowed to post images :(
But my question is can I draw a triangle strip that is, in effect, longer than one "tile" but map a different area of the texture to that "tile".
So instead of drawing a triangle strip pretending to be a quad, one at a time for each tile, can I somehow draw a whole row of the tilemap (like 1,2,3,4 and cleverly shift around the texture coordinates so each "tile" is now from a different area of the texture? So for example I draw a triangle strip 4 tiles long but shift the texture coordinates so the first "tile" is the yellow of my texture the second red ... third blue... etc
If I've not explained myself too well apologies!
It might just be that this is not possible and I have to draw each one individually which seems like I've saved effort with an atlas, then had to draw them all out slowly anyway regardless. Hmm.
Sure, just adjust texture coordinates, that is how texture atlases work.