This is because alpha blending is applied to the pixel color that's present at the time of rendering the transparent poly. If you draw something else later on that's further away gl will ignore it based on the z buffer.
To prevent this you need to render all solid things before you render any transparent stuff. You also might need to sort individual poly/parts when using multiple transparent colors in a single scene. If you don't do that the colors won't blend naturally.
To prevent this you need to render all solid things before you render any transparent stuff. You also might need to sort individual poly/parts when using multiple transparent colors in a single scene. If you don't do that the colors won't blend naturally.