The worship dealt with in the Agama texts necessarily involves worship-worthy images. The rituals and sequences elaborated in the Agama texts are in the context of such worship-worthy image, which necessarily has to be contained in a shrine. The basic idea is that a temple must be built for the icon,and not an icon got ready for the temples; for, a temple is only an outgrowth of the icon; an expanded image of the icon. And an icon is meaningful only in the context of a shrine that is worthy to house it. That is how the Agama literature makes its presence felt in the Shilpa-Sastra, Architecture. The icon and its form; the temple and its structure; and, the rituals and their details, thus get interrelated . Further, the Indian temples should be viewed in the general framework of temple culture; which include not only religious and philosophical aspects but also the social, aesthetic and economic aspects .
Elaborate rules are laid out in the Agamas for Shilpa ; describing the quality requirements of the places where temples are to be built; the kind of images to be installed; the materials from which they are to be made; their dimensions, proportions; air circulation; lighting in the temple complex etc. The Manasara and Shilpasara are some of the works dealing with these rules. The rituals followed in worship services each day at the temple also follow rules laid out in the Agamas.
While describing the essential requirements for a place of pilgrimage , Shilpa Shatras of the Agamas elaborate on the requirements of the temple site; building materials; dimensions, directions and orientations of the temple structures; the image and its specifications. The principal elements that are involved are the Sthala (temple site); Teertha (Temple tank); and, Murthi (the idol). A temple could also be associated with a tree, called the Sthala Vriksham.
The Gupta Age marked the advent of a vibrant period of building and sculpting activities. The texts of this period such as the Arthashastra of Kautilya and Matsya Purana included chapters on the architecture of the way of summary. By the end of the period, the art and craft flourished; and branched into different schools of architectural thought; but, all were based on common underlying principles. These principles are now part of Vastushastra, the science of architectural design and construction. . It is explained that the term Vastu is derived from Vasu meaning the Earth principle (prithvi). This planet is Vastu; and, whatever that is created is Vastu; and , all objects of earth and those surrounding it are Vastu.
During the medieval period, vast body of Sanskrit references, independent architectural manuals were written, without reservation or uniformity; and were scattered across the country. Apparently, later, some attempts were made to classify and evaluate their contents in a systematic way. Of the many such attempts that tried to bring about order and coherence in the various theories and principles of temple construction, the most well known compilations are Manasara and Mayamata. They are the standard texts on Vastu Shastra; and , they codify the theoretical aspects of all types of constructions; but specifically of temple construction. These texts deal with the whole range of architectural science including topics such as soil testing techniques, orientation, measures and proportion, divination, astrology and ceremonies associated with the construction of buildings.
Manasara is a comprehensive treaty on architecture and iconography. It represents the universality of Vastu tradition; and includes the iconography of Jain and Buddhist images. The work is treated as a source book and consulted by all.
The Mayamata too occupies an important position. It is a general treatise on Vastu shastra; and, is a text of Southern India. It is regarded a part of Shaiva literature ; and, it might belong to the Chola period when temple architecture reached its peak. It is the best known work on Vastu. The work is coherent and well structured. It defines Vastu as the arrangement of space, anywhere, wherein the immortals and mortals live.
These subjects are intertwined with Astrology. The Vastu Texts believe that Vigraha (icon or image of the deity) is closely related to Graha (planets).The term Graha literally means that which attracts or receives; and, Vigraha is that which transmits. It is believed that the idols receive power from the planets; and transmit the power so received. It not merely is a symbolism; but, it is also the one that provides logic for placement of various deities in their respective quarters and directions within the temple complex.
The texts that are collectively called Vastu Shastra have their origin in the Sutras, Puranas and Agamas; besides the Tantric literature and the Brhat-Samhita of Varahamihira (52 vāstuvidyā).
The Vastu texts classify the temple into three basic structures: Nagara, Dravida and Vesara. They employ, respectively, the square, octagon and the apse or circle in their plan. These three styles do not pertain strictly to three different regions ; but, are three schools of temple architecture that might be employed commonly. The Vesara, for instance, which prevailed mostly in western Deccan and south Karnataka, was a derivation from the apsidal chapels of the early Buddhist period which the Brahmanical faith adopted and vastly improved.
These three schools have given rise to about forty-five basic varieties of temples types. They too have their many variations ; and, thus the styles of temple architecture in India are quite diverse and virtually unlimited .