Wikitude

Hello,

my apologies for the late response. Would it be possible for me to see a screenshot of the incorrect rendering? I'm afraid I don't have the time to have a closer look at your code currently. I'm hoping having a look at the problem visually might be revealing.

- Daniel

Good morning,

that's interesting. Is the little cross being tracked correctly (staying in the center of the target when the camera or taget is moved)?

- Daniel

Hi,

if the target is being tracked correctly, the pose can't be that wrong. I would recommend that you have a look at the "CustomCamera" plugin sample. It does exactly what you are trying to do; it renders a simple quad as an augmentation from within the plugin on an image target using getModelViewMatrix. You should actually be able to directly copy&paste most of the code. Don't be intimidated by the amount of rendering code, most of it pertains to the fullscreen effect that is being rendered.

I just ran the sample and found it to be working correctly.

Here's the relevant excerpt:

const float TARGET_HEIGHT_IN_PIXELS = 320.0f;
            
wikitude::sdk::Matrix4 toSizeInPixelsScaling;

// scaled to be able to re-use the screen aligned quad (side length = 2) and thus
// avoid having to create additional vertex data and correspondig code
toSizeInPixelsScaling.scale(0.5f, 0.5f, 1.0f);
            
toSizeInPixelsScaling.scale(TARGET_HEIGHT_IN_PIXELS, TARGET_HEIGHT_IN_PIXELS, 1.0f);
            
wikitude::sdk::Matrix4 modelView = targetToDraw.getModelViewMatrix();
wikitude::sdk::Matrix4 projection = targetToDraw.getProjectionMatrix();

wikitude::sdk::Matrix4 scaleMatrix;
scaleMatrix.scale(targetToDraw.getTargetScale().x, targetToDraw.getTargetScale().y, 1.0);
            
wikitude::sdk::Matrix4 modelViewProjection = projection * modelView * scaleMatrix * toSizeInPixelsScaling;
            
WT_GL_ASSERT(glUseProgram(_augmentationShaderHandle));
GLint modelViewProjectionLocation;
WT_GL_ASSERT_AND_RETURN(modelViewProjectionLocation, glGetUniformLocation(_augmentationShaderHandle, "uModelViewProjectionMatrix"));
WT_GL_ASSERT(glUniformMatrix4fv(modelViewProjectionLocation, 1, GL_FALSE, modelViewProjection.get()));
            
setVertexAttributes(_augmentationShaderHandle);
            
WT_GL_ASSERT(glDrawElements(GL_TRIANGLES, sizeof(_indices)/sizeof(_indices[0]), GL_UNSIGNED_SHORT, 0));

- Daniel

Here's a small video demonstrating what the sample does. The solidly coloured rectangle is rendered from within the plugin.

- Daniel

Good morning,

the pose is set up in a way such that you need to apply it to an augmentation in the pixel coordinates of the image target. The value 320 is simply the height of the surfer target as can be seen in the screenshot I attached. For targets of different size you would need to change this value accordingly.

Applying the value as a scale simply turns the [-0.5, 0.5] quad into a [-TARGET_HEIGHT/2, TARGET_HEIGHT/2] quad.

Can't say I remember why it is set up like that, but I'm sure there some legacy reason for it.

- Daniel