I am trying to add a transparent texture on top a cube. Only the front face is not transparent. Other sides are transparent. What could be the problem?. Any help is appreciated.
EDIT : I found that the face which is drawn first is opaque.
3 face of the cube is drawn.
Opaque face.((This face's index is given first in GLdrawElements))
Transparent face.
You most probably ran into a sorting problem. To display transparent geometries correctly the faces of the object have to be sorted from back to front.
Unfortunately there is no built-in support for that in opengl-es (or in any gfx-library in existance). The only possibility is to sort your polygons, recreate your object each frame and draw it with correctly ordered faces.
A workaround would be using additive transparency instead of normal transparency. Additive transparency is an order independent calculation. You have to remember to turn off z-buffer writes while drawing because otherwise some geometry may be ocluded.
Additive transparency is achieved by setting both blendfunc values to GL_ONE.
Related
I am using Unity 5 to develop a game. I'm still learning, so this may be a dumb question. I have read about Depth Buffer and Depth Texture, but I cannot seem to understand if that applies here or not.
My setting is simple: I create a grid using several quads (40x40) which I use to snap buildings. Those buildings also have a base, made with quads. Every time I put one one the map, the Quads overlap and they look like the picture.
As you can see, the red quad is "merging" with the floor (white quads).
How can I make sure Unity renders the red one first, and the white ones are background? Of course, I can change the red quad Y position, but that seems like the wrong way of solving this.
This is a common issue, called Z-Fighting.
Usually you can reduce it by reducing the range of “Clipping Planes” of the camera, but in your case the quads are at the same Y position, so you can’t avoid it without changing the Y position.
I don't know if it is an option for you, but if you use SpriteRenderer (Unity 2D) you don’t have that problem and you can just set “Sorting Layer” or “Order in Layer” if you want modify the rendering order.
In my scene, the smileys(Quad with png image) are placed at Y:0 and the dots(Quad with tiling 3X3) are placed at Y: -0.25.
The shader I need to use for the smileys is Transparent-Diffuse as I am using a circle png image.
But the dots I use below are showing up above the smiley. Using any other shader like Diffuse solves the issue but the smiley becomes a square.
Screenshot:
If you need any more clarifications please dont hesitate to ask.
Edit:
I have attached the shader details of both the smiley and the dots from the inspector panel.
link: http://postimg.org/image/cvws1os7d/
Edit 2:
I have found that the issue should be with the MainCamera and especially with distance & "Field Of View".
I need to use "Perspective" as projection type and 140 as Field of View.
If I change the projection type to Orthographic the issue is completely fixed.
The below screenshots show how the distance and Field of View controls the appearance of the dots over the smiley.
Screenshot 1:
Y position: 8.48
Field of View: 30
link: http://postimg.org/image/s31tttrkp/
Screenshot 2:
Y position: 9.7
Field of View: 30
link: http://postimg.org/image/f71sq0y4b/
Screenshot 3:
Y position: 11.41
Field of View: 30
link: http://postimg.org/image/3uk4az3d3/
Screenshot 4:
Y position: 1
Field of View: 140
link: http://postimg.org/image/bul9zwg7z/
Can this be a clue?
Just a couple of info, on how transparency is typically implemented (not only by Unity).
Meanwhile opaque objects can be drawn in any order (even if sorting them in front-to-back order can eventually improve some GPU performances relying on an early z-cull). Which pixels are visible can be deduced using the depth value stored into the z-buffer.
You can't rely on z-buffer for transparency.
For rendering translucent objects a typical approach is to draw them after all opaque objects, and sorting them in back-to-front order (transparent objects more distant from the camera are drawn first).
Now the question is: how do you sort objects? with a perspective camera and meshes of a generic shape, the solution is not obvious.
For quad meshes oriented parallel to a ortographic camera view plane, the z order is implicitly correct (that's why it always works for you).
You can also notice that camera position influences the drawing order, because with perspective camera the order is calculated as distance between object position and camera.
So what can you do with Unity3d, in your specific use case scenario?
A couple of tricks:
Explicitly set the render queue of the material
Explicitly set the render order inside the shader (similar of the above, but equals to every object with the same shader)
Fake the depth using Offset into the shader (not that useful in your case but worth to be known)
hope this helps
EDIT
I didn't know that, the camera transparency sorting mode appears to be customizable. So this is another solution, maybe the best for your case if you want to use a perspective camera.
If you are using Sprite Renderer component to render the images, you have to change the rendering order with Sorting Layer and Order in Layer parameters instead of changing the Y position.
Sorting layers can be added by clicking the "default" and choosing "Add Sorting Layer..". The order of the layers is changed by dragging them into different order. With Order in Layer lower numbers are rendered first. This means that higher numbers will be drawn on top of lower ones.
I'm looking for a way to dynamically change a part of a Quad that has a SpriteRenderer attached to it. Let's say I have a red Quad and a blue Quad, and then I drag one onto the other (fast or slow), the intersecting part should be colored using a green sprite. This illustration shows the scenario I'm trying to solve.
Can someone please help me with this?
You have two options:
First, if your mid color will be the correct mixture of other two color, in this case it would be yellow, you can use Mobile Particle/Additive or Mobile Particle/Multiply Shaders.
In a second way, you can write your own shader that takes the intersection area as parameter and paint your textures according to parameters.
I'm drawing irregular shapes using Core Graphics on a retina display. I do this by creating a UIBezierPath with 5 to 10 random points. In drawRect I stroke the path and fill it using solid red colour.
My problem is that diagonal lines in my drawing doesn't appear to be sharp.
I have tried anti aliasing but if anything this makes it appear worse. I have experimented with different line widths, not stroking, not filling, but I can not seem to get a really sharp diagonal line.
For comparison I created a similar shape in Photoshop (using similar size) and saved that as PNG. If I display that PNG on iOS it looks much sharper.
What can I do to make my shape that I create in code look sharp?
Make sure your CGPoint's are rounded to the nearest integer value.
Say the user taps 4 spots on the iphone, defining an irregular 4 sided polygon (in 2d space). Is there a way to map/fit a (potentially highly distorted) image onto this shape, without using OpenGL?
Something like:
Is my only option to somehow calculate the 3d space that my irregular 4 sided shape sits in (based on where the tapped 2d points sit), create an OpenGL plane in that space, and map my texture to it flatly? Seems like there should be an easier way...
Thanks in advance.
Update: After diving into OpenGL I'm almost there... but I still can't get the texture to distort correctly. The triangulation seems to be messing with the texture mapping:
I can't answer your question completely, but one thing I would say is that you don't need to think about any conversion / mapping to 3D. Using OpenGL you can easily draw the shape in 2D and have the texture mapped as you desire. No need for any fancy maths or conversions. It's no more complicated than drawing a rectangle. OpenGL doesn't care that your 4-sided shape isn't actually rectangular.