Undoubtedly, when the term pixel is mentioned immediately most users relate it to digital images and computer screens and computer devices, and the fact is that the concept behind the word pixel is related to this, but its scope is much broader.
However, the truth is that within the universe referred to digital images there are also other terms that are used to define certain elements that make up that image, among which are megapixels, texel and voxel.
Although we have probably heard these words mentioned on several occasions, the truth is that most users are unaware of the fundamental concept contained in each of these terms.
In order to understand the role that each one of these concepts plays within a digital image, in principle we must be clear that in order to be able to represent graphics or images in a computer we can resort to two main ways of doing it, through vector or through raster.
In the case of vector graphics, these graph images through the use of mathematical equations, with which it is possible to represent various shapes with lines, lines and curves.
In the case of raster graphics, the image is represented through a matrix of color values, which are placed next to each other in a grid pattern.
Besides, in order to know the concept behind the words pixel, texel and voxel, it is important to review some items related to the so-called image resolution. Basically, when we talk about digital image resolution we refer to the quality of a photograph we have taken with our cell phone or our digital camera.
This is generally correct, since image resolution is definitely the level of detail that an image has, whether it is a photographic or a video image. For this reason, the resolution of a digital photograph will depend on the density of the individual components of the image. These components are called pixels
In order to be able to appreciate even the smallest details in a photograph, the ideal is to be able to capture a photo that contains as many details as its original source. That is why we could summarize that the pixel is extremely important in terms of image quality, since the more pixels, the higher the resolution of the image in question.
Therefore, we will not be able to increase the resolution of the image just by enlarging it, but we will be producing the opposite effect, because if we enlarge an image at the same time we are enlarging the size of the pixels that make up the image, which will make these pixels more evident and will significantly reduce the quality of the image when it is displayed.
Having clear the concept of the importance of the so-called pixel within a digital image in relation to the resolution and quality of that image, we can already start reviewing what the terms pixel, megapixel, texel and voxel mean.
What is a Pixel?
The term pixel has been coined for some decades, specifically since the digital image has originated, since it comes from the acronym of the concept in English “Picture Element”, which in Spanish means image element.
Basically, we could say that the pixel is the smallest homogeneous colour unit that makes up the digital image. Hence, when we observe and talk about a digital photograph, a video or other, we refer to its pixels.
Therefore, the concept of pixel refers to the points that are used within a set in order to show an image within a screen or a printed image, and that is why the term can be used to refer to the smallest unit of an image.
However, at this point it is important to clarify that the pixel is not a measure of size, so when the term is used in that way, we are actually making a misconception.
This confusion that is generated in most users is usually given by the information around digital cameras, since manufacturers usually offer the buyer of a camera data related to a measurement of pixels per inch, known as PPI.
When the user reads this information, he thinks that it refers to a certain size of the image, but the truth is that it means the amount of pixels embedded in the image that we will create with the camera. Of course, it is correct that the amount of pixels will determine the quality that the captured image will have in its visualization.
Besides referring to the points that make up a digital image, the pixels are also related to the screens, since they are made up of several million pixels, which are arranged in a grid.
In this sense, we can see that the resolution of a screen is usually given in terms of the amount of image elements available in each direction of the screen, so a screen that indicates that it has a resolution of 1024 x 768, what we are referring to is that it has 1,024 pixels wide and 768 pixels high.
On the other hand, it is important to mention that for the visualization of what we see on a computer or telephone screen to have the appropriate characteristics, the pixels are formed in addition to other smaller elements, since each pixel includes three points inside, one red, one blue and one green, which we call the RGB standard.
These three points that are part of a pixel, converge in the same point, giving the possibility of completing the color and shape assigned to each pixel within an image.
At this point we must talk about the so-called pixel density, a concept that refers to the amount of pixels that a certain space of a digital image has, so that ultimately the information about the pixel density will indicate us the amount of elements that make up an image.
For this reason, and as we mentioned before, the higher the density of pixels, the higher the quality of the image. This is mainly due to the fact that the higher the amount of pixels in a certain space, the higher the resolution of the image can be achieved, which results in being able to achieve more detail.
That’s why in the end the image quality will depend on the amount of pixels that a digital camera can capture, that is to say the resolution that it will give when generating the photograph, which as we saw is generally measured in PPI (pixels per inch).
As an example of this, we could point out that a standard photo of those used in the field of commercial photography, having a size of around 20 x 25 centimeters, with a resolution of 300 PPI, would be made up of 7.2 million pixels.
But we must also bear in mind that when we talk about digital cameras, we will see that in general most manufacturers have replaced the term pixels with megapixels, which they use to describe the resolution that a camera has to capture photographs.
In this context, the resolution that a camera can provide in its photos is usually given in terms of two dimensions, for example 1600 x 1200, indicating a width and height for the image, which results from the total sum of pixels generated by multiplying the two dimensions.
The calculation in the case that a digital camera can capture photographs in a resolution of 1600 x 1200, then refers to the equipment is capable of generating images that would include 1,920,000 pixels, or 1.9 megapixels.
What is a MegaPixel?
In principle, it is important to note that when referring to the megapixels of a digital image, we are talking about a measure that corresponds to that image. In this sense, a megapixel, which is usually expressed by the abbreviation Mpx, is equivalent to 1 million pixels, and therefore is a term used in the field of digital cameras, in order to provide the user with an indication of the resolution capacity that the equipment can throw when capturing an image.
That is why we surely all know that the term megapixel is frequently used to define the amount of image resolution that different models of digital cameras have, which results from a mathematical formula that allows us to know the amount of pixels and therefore resolution.
Essentially, in the case of digital cameras, the number of megapixels will express the resulting size of the photographs taken with that equipment. Therefore, the greater the number of megapixels, the higher the quality we can obtain from the image and the same goes for the size of the image.
For this reason, the term megapixel is used in relation to the quality offered by a digital camera, so if for example we have a camera that can capture images in 3.1 megapixels, what we will be indicating with this information is that the equipment is capable of capturing photos with a resolution of 2048 x 1536, which is equivalent to 3,145,728 pixels, ie 3.1 megapixels.
Therefore, we can conclude that the greater the number of megapixels offered by a digital camera, the higher the resolution of the image, that is, we will obtain a better quality of the image, with much greater detail.
Bearing in mind these parameters, we now know that when we buy a digital camera we must carefully observe the amount of megapixels it can offer. Of course, the choice of camera will depend on our needs.
For example, if we require a digital camera that offers us images that can later be visualized on a screen and we do not need to print those photos, then it will not be necessary for us to acquire a camera with a large amount of megapixels, since from 1.5 megapixels, its visualization on the screen will be more than adequate.
However, in the case we need to print the photos captured with the digital camera, then we recommend a computer that reaches 4 or 5 megapixels, ie have a resolution of about 2500 x 2000 or more. Keep in mind that most professional photographers tend to opt for equipment that goes beyond 11 megapixels.
What is Texel?
The term Texel has emerged from the union of the concept in English “Texture element” or “Texture pixel”, and basically it is the smallest unit of texture that is applied to a surface of the digital image.
Therefore, we could roughly say that in the case of a digital image it is represented by a set of pixels, while in the case of a texture, it is represented by a group of texels. This is why this term is used almost exclusively for computer graphics.
It should be noted that while the text can correspond to several pixels, it can also be less than one pixel, so they are generally not visible to the human eye. Basically, a Texel is simply a pixel within an image texture.
Texels are usually assigned to pixels to make up the final image of a picture where a texture has been incorporated into a 3D graphic surface, which is commonly called texture mapping.
Therefore, we can say that if the images are represented by sets of pixels, then we can also say that the textures are represented by sets of Texels.
When the procedure known as texture mapping is performed, that is, a surface or a 3D graphic is textured, what happens is that the renderer assigns Texels to the appropriate pixels in order to represent the output image that will be possible to visualize.
In addition, when a texture is made, the so-called filtering is usually used, which is a method that is applied in order to be able to fill the spaces that may be left empty between the texts that make up the texture, and in this way the possibility of borders appearing that may be visible between the texts is avoided.
On the other hand, we must bear in mind that in the case of texels, an extremely important piece of information is the filling rate, information that will indicate how many texels can be processed per second, and in this way we can know, for example, the performance of the computer equipment used for this purpose, basically of the graphic card.
The fill rate numbers are usually expressed in megapixels/sec or megatexels/sec, and its main function is to inform us the number of finished pixels that are written in the frame buffer.
Of course, megatexels are usually used in the creation of 3D graphics mainly in the most modern video games, where even today we can find the use of several layers of multiple texture effects.
The lighting, the shadows, the textures, in short all these elements that are part of modern video games and that perhaps we do not pay adequate attention, are created from a set of texts that are part of the texture space that will give the possibility of expressing a graphic visually.
What is Voxel?
Voxel is a term that comes from the English “Volumetric pixel” and refers to the cubic unit that is part of a three-dimensional object, and is the smallest unit of a three-dimensional set that can be processed. For this reason, voxel basically refers to the equivalent of the pixel in a 2D object.
In general, graphics and images using voxels are often used in the medical field, in complex computer studies, such as computed tomography, magnetic resonance imaging, and so on.
Through this method, healthcare professionals can access a complete three-dimensional image of their patient’s body.
Today, the use of voxel is also often applied to other fields, such as engineering, the film industry and video game development, among others.
If we take the literal meaning in English of voxel, then we get the words “volume” and “pixel”, that is to say that ultimately a voxel is a volumetric pixel. But we must also take into account that if a pixel is a two-dimensional square, a voxel is a three-dimensional cube.
Basically, a voxel is a single cube placed within a three-dimensional grid, with only one color value assigned. For this reason, all voxels that make up the image are the same size.
However, in a grid, the voxels can be placed in different positions with different colors, in order to form the so-called voxel model.
Due to their characteristics, many people call Voxels as 3D pixels, since their behavior is similar to that of pixels, although the big difference between them is that pixels exist in a 2D grid, while Voxels exist in a 3D grid.
Pixels, texels, voxels and so on
Now that we know the basic concept in relation to pixels, texels and voxels, we can point out that within the scope of computer graphics, each one of them has a well-defined and specific role to play in representing what we can visualize on a screen.
In this sense, we can summarize by saying that a pixel is the smallest addressable point on a screen, while a texel is the smallest unit of what is being drawn on the screen, and a voxel is the smallest unit of 3D space being drawn.
In practice, let’s imagine that we are drawing on our computer a very simple shape, for example a square of 100 pixels by 100 pixels. In that drawn object, the resulting square is 1 texel by 1 texel, since in that graphic representation the texel we use is 100 pixels.
If we add perspective to the square we have drawn, which becomes a cube, which we also accompany with other cubes that allow us to create a space that would be the representation of a 3D field of vision, it is there where the voxel appears, which is ultimately the smallest unit of 3D space defined in the drawing.